JP7127325B2 - Slurry for thermally crosslinked lithium ion battery and method for producing the same, electrode for lithium ion battery, separator for lithium ion battery, separator/electrode laminate for lithium ion battery, and lithium ion battery - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a slurry for a thermally crosslinked 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, lightweight, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. Therefore, in recent years, improvements in battery members such as electrodes and separators have been studied for the purpose of further improving the performance of lithium ion batteries.

For both the positive electrode and the negative electrode of a lithium ion battery, an electrode active material and a binder resin are dispersed in a solvent to form a slurry, which is coated on both sides of a current collector (for example, a metal foil), and the solvent is removed by drying to form an electrode. After forming the layers, it is manufactured by compression molding with a roll press machine or the like.

In recent years, various electrode active materials have been proposed as electrode active materials for electrodes for lithium ion batteries from the viewpoint of increasing battery capacity. However, depending on the electrode active material, it is easy to expand and contract with charging and discharging. As a result, the electrode for lithium ion batteries undergoes a volume change (springback property) from the initial stage of repeated charging and discharging, and there is a problem that the electrical characteristics such as cycle characteristics of lithium ion batteries using this tend to deteriorate. there is

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

In recent years, heat-resistant separators have been proposed for lithium-ion batteries, 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. It is known that the coating layer has the effect of suppressing shrinkage of the separator even when exposed to high temperatures. 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 during transportation on the production line or inside the battery cell, and it is easy to fall off. rice field.

Therefore, in the field, studies have been made to solve the above problems with binder resins. For example, a separator characterized by containing a polyacrylic acid salt in which polyacrylic acid is crosslinked with a metal cation (Patent Document 3) has also been proposed. It is Moreover, a porous membrane composition for lithium ion secondary batteries containing a water-soluble thickener containing a carboxyl group, a carbodiimide compound cross-linking agent, and a particulate polymer has been proposed (Patent Document 4).

WO2016/159198 JP 2015-185530 A JP 2016-012478 A Japanese Patent No. 6187464

Regarding the electrode of a lithium ion battery, Patent Document 1 proposes a crosslinked emulsion, which increases the degree of crosslinkage, but is insufficient in springback resistance.

The N-methylolacrylamide described in Patent Document 2 has a problem of gelation because the resin itself has crosslinkability. Therefore, the introduction amount cannot be increased and the degree of cross-linking cannot be increased, so the effect of springback resistance is insufficient.

Regarding the separator of the lithium ion battery, the polyacrylic acid salt described in Patent Document 3, in which polyacrylic acid is crosslinked with metal cations, has a problem that the effect of improving adhesion is low because the crosslinking effect is extremely low.

Patent Document 4 proposes a porous layer for a separator 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 slurry has poor stability and tends to gel easily. As a result, fine particles agglomerate 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 properties to a lithium ion battery, as well as excellent heat shrinkage resistance, powder falling resistance, substrate adhesion, rate characteristics , to provide a separator capable of imparting output characteristics to a lithium-ion battery. In the present disclosure, the powder-off resistance means the binding property between ceramic fine particles, and the substrate adhesion means the layer obtained by coating the substrate and the slurry according to the present invention on the substrate and drying it ( coating layer).

As a result of intensive studies to solve the above problems, the present inventors have developed a slurry for a thermally crosslinked lithium ion battery containing poly(meth)acrylamide produced using a specific monomer, a water-soluble cross-linking agent, and water. The inventors have found that the above problems can be solved by using them, and have completed the present invention.

The following items are provided by this disclosure.
(Item 1)
a water-soluble poly(meth)acrylamide (A) containing 50 mol% or more of structural units derived from the N-unsubstituted or monosubstituted (meth)acrylamide group-containing compound (a) based on 100 mol% of the structural units;
a water-soluble cross-linking agent (A1) comprising one or more selected from the group consisting of formaldehyde, glyoxal, hexamethylenetetramine, urea-formaldehyde resins, and methylolmelamine resins;
and water for a thermally crosslinked lithium ion battery.
(Item 2)
The water-soluble cross-linking agent (A1) is added to 0 with respect to 100% by mass of structural units derived from the N-unsubstituted or monosubstituted (meth)acrylamide group-containing compound (a) in the water-soluble poly(meth)acrylamide (A). 001 to 3.0% by mass of the slurry for a thermally crosslinked lithium ion battery according to the above items.
(Item 3)
The slurry for a thermally crosslinked lithium ion battery according to the above items, comprising an electrode active material (B).
(Item 4)
The slurry for a thermally crosslinked lithium ion battery according to any of the above items, wherein the electrode active material (B) contains 10% by mass or more of silicon or silicon oxide.
(Item 5)
The slurry for a thermally crosslinked lithium ion battery according to the above items, which contains ceramic fine particles (C).
(Item 6)
The method for producing a slurry for a thermally crosslinked lithium ion battery according to any one of the above items, comprising adding the water-soluble cross-linking agent (A1) to the aqueous solution containing the water-soluble poly(meth)acrylamide (A). .
(Item 7)
A lithium ion battery electrode obtained by applying the thermally crosslinkable lithium ion battery slurry according to any one of the above items to a current collector and causing a thermal crosslinking reaction.
(Item 8)
A lithium ion battery comprising the lithium ion battery electrode according to any of the above items.
(Item 9)
A separator for a lithium ion battery obtained by coating a porous polyolefin resin base material or a plastic nonwoven fabric with the thermally crosslinkable lithium ion battery slurry according to the above items and thermally crosslinking the substrate.
(Item 10)
The slurry for thermal cross-linking type lithium ion battery described in the above items,
A separator/electrode laminate for a lithium ion battery, obtained by coating an electrode material on the active material side and thermally crosslinking the electrode material.
(Item 11)
A lithium ion battery comprising the lithium ion battery separator according to the above item and/or the lithium ion battery separator/electrode laminate according to the above item.

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

By using the aqueous binder solution for lithium ion batteries and the slurry for lithium ion batteries of the present invention, it is possible to provide a lithium ion battery with improved battery capacity sustainability and springback resistance.

By using the aqueous binder solution for lithium ion batteries and the slurry for lithium ion batteries of the present invention, there is provided a separator for lithium ion batteries with improved heat shrinkage resistance, powder drop resistance, substrate adhesion, rate characteristics, and output characteristics. can.

Throughout the present disclosure, the range of numerical values for each physical property value, content, etc. can be set as appropriate (for example, by selecting from the upper and lower limit values described in each item below). Specifically, for the numerical value α, when the upper limit of the numerical value α is A1, A2, A3, etc., and the lower limit of the numerical value α is 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. Slurry for thermal cross-linking lithium ion battery: Slurry for lithium ion battery, also called slurry]
The present disclosure provides a water-soluble poly(meth)acrylamide (A) containing 50 mol% or more of structural units derived from an N-unsubstituted or monosubstituted (meth)acrylamide group-containing compound (a) based on 100 mol% of structural units,
a water-soluble cross-linking agent (A1) comprising one or more selected from the group consisting of formaldehyde, glyoxal, hexamethylenetetramine, urea-formaldehyde resins, and methylolmelamine resins;
and a slurry for a thermally crosslinked lithium ion battery comprising water.

In this disclosure, "slurry" means a suspension of liquid and solid particles.

In the present disclosure, “water-soluble” means that the insoluble content is less than 0.5% by mass (less than 2.5 mg) when 0.5 g of the compound is dissolved in 100 g of water at 25 ° C. 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 group of monomers containing a (meth)acrylamide group-containing compound.

In the present disclosure, "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 atom on the nitrogen of the (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.

［式中、Ｒ^Ａ１は水素又はメチル基であり、Ｒ^Ａ２とＲ^Ａ３は一方が水素であり、もう一方は、水素、置換若しくは非置換のアルキル基、アセチル基、又はスルホン酸基であり、Ｒ^Ａ４及びＲ^Ａ５はそれぞれ独立して、水素原子、置換若しくは非置換のアルキル基、カルボキシル基、ヒドロキシ基、アミノ基＜－ＮＲ^ＡａＲ^Ａｂ（Ｒ^Ａａ及びＲ^Ａｂはそれぞれ独立して水素又は置換若しくは非置換のアルキル基である）＞、アセチル基、スルホン酸基等が例示される。］
により表わされる化合物等が例示される。 The N-unsubstituted or monosubstituted (meth)acrylamide group-containing compound (a) has the following structural formula

[In the formula, 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 each independently represents 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 or an unsubstituted alkyl group)>, an acetyl group, a sulfonic acid group, and the like. ]
Compounds represented by are exemplified.

Alkyl groups are exemplified by linear alkyl groups, branched alkyl groups, cycloalkyl groups and the like.

A straight-chain alkyl group is represented by a general formula of -C _n H _2n+1 (n is an integer of 1 or more). Linear alkyl groups include methyl group, ethyl group, propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decamethyl group, etc. are exemplified.

A branched alkyl group is a group in which at least one hydrogen of a straight-chain alkyl group has been replaced by an alkyl group. Branched alkyl groups are exemplified by diethylpentyl, trimethylbutyl, trimethylpentyl, trimethylhexyl and the like.

The cycloalkyl group is exemplified by a monocyclic cycloalkyl group, a bridged ring cycloalkyl group, a condensed ring cycloalkyl group and the like.

In the present disclosure, monocyclic means a cyclic structure with no internal bridging structure formed by covalent carbon bonds. Fused rings also refer to cyclic structures in which two or more single rings share two atoms (ie, each ring shares (condenses) only one edge with each other). Bridged ring means a cyclic structure in which two or more single rings share three or more atoms.

Monocyclic cycloalkyl groups are exemplified by cyclopentyl, cyclohexyl, cycloheptyl, cyclodecyl and 3,5,5-trimethylcyclohexyl groups.

The bridging ring cycloalkyl group is exemplified by a tricyclodecyl group, an adamantyl group, a norbornyl group and the like.

The condensed ring cycloalkyl group is exemplified by a bicyclodecyl group and the like.

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

N-monosubstituted (meth)acrylamide group-containing compounds include 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)acrylamidosulfonic acid, and salts thereof.

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

In one embodiment, the upper limit of the proportion of structural units 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 limits are 99.8, 99.7, 99.2, 95, 90 , 85, 80, 75, 70, 65, 60, 55, 50 mol % and the like are exemplified. In one embodiment, the proportion of the structural unit 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 structural units 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 to 100% by weight is preferred, 45 to 100% by weight is more preferred, and 50 to 100% by weight is particularly preferred.

Good dispersibility of electrode active materials, fillers, ceramic fine particles, etc., by containing a specific amount of constituent units derived from the N-unsubstituted or monosubstituted (meth)acrylamide group-containing compound (a) in the component (A) As a result, uniform layers (electrode active material layer, ceramic fine particle layer, etc.) can be produced, which eliminates structural defects and exhibits good charge/discharge characteristics. Further, by including a specific amount of constituent units derived from a (meth)acrylamide group-containing compound in the component (A), the oxidation resistance and reduction resistance of the polymer are improved, and deterioration at high voltage is suppressed. It shows good charge/discharge durability.

(monomers other than component (a): also referred to as component (b))
In the above monomer group, monomers (component (b)) other than component (a) can be used as long as the desired effects of the present invention are not impaired. As the component (b), various known components may be used alone, or two or more thereof may be used in combination.

Component (b) includes N,N-disubstituted (meth)acrylamide group-containing compounds, unsaturated carboxylic acids, unsaturated sulfonic acids, unsaturated phosphoric acid and other acid group-containing monomers, unsaturated carboxylic acid esters, α , β-unsaturated nitriles, conjugated dienes, aromatic vinyl compounds, and the like.

（式中、Ｒ^Ｂ１は水素又はメチル基であり、Ｒ^Ｂ２及びＲ^Ｂ３はそれぞれ独立して、置換若しくは非置換のアルキル基、アセチル基、又はスルホン酸基であるか、或いはＲ^Ｂ２及びＲ^Ｂ３が一緒になって環構造を形成する基であり、Ｒ^Ｂ４及びＲ^Ｂ５はそれぞれ独立して、水素、置換若しくは非置換のアルキル基、カルボキシル基、ヒドロキシ基、アミノ基（－ＮＲ^ＢａＲ^Ｂｂ（Ｒ^Ｂａ及びＲ^Ｂｂはそれぞれ独立して水素又は置換若しくは非置換のアルキル基である））、アセチル基、スルホン酸基である。置換アルキル基の置換基はヒドロキシ基、アミノ基、アセチル基、スルホン酸基等が例示される。また、Ｒ^Ｂ２及びＲ^Ｂ３が一緒になって環構造を形成する基は、モルホリル基等が例示される。）
により表現される化合物等が例示される。 The N,N-disubstituted (meth)acrylamide group-containing compound has the following structural formula

(In the formula, R ^B1 is hydrogen or a methyl group, 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 is a group that together form a ring structure, and each of R ^B4 and R ^B5 is independently hydrogen, a substituted or unsubstituted alkyl group, a carboxyl group, a hydroxy group, an amino group (-NR ^Ba R ^Bb ( Each of R ^Ba and R ^Bb is independently hydrogen or a substituted or unsubstituted alkyl group)), an acetyl group, a sulfonic acid group, and the substituents of the substituted alkyl group are a hydroxy group, an amino group, an acetyl group, and a sulfone group. Examples include an acid group, etc. Further, the group in which R ^B2 and R ^B3 together form a ring structure is exemplified by a morpholyl group, etc.)
A compound represented by is exemplified.

The above N,N-disubstituted (meth)acrylamide group-containing compounds include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, ( meth)acryloylmorpholine, salts thereof and the like are exemplified. Salts are exemplified by those mentioned above.

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

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

Examples of unsaturated carboxylic acids 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 units is not particularly limited. Less than mol % (eg less than 30, 20, 19, 15, 10, 5, 1 mol %, 0 mol %) is preferred.

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, etc., and the lower limit is 50, 40, 30, 20, 10, 5, 1, 0% by mass and the like are exemplified. In one embodiment, the unsaturated carboxylic acid content is preferably 0.0 to 60% by mass relative to 100% by mass of structural units.

Unsaturated sulfonic acids include α,β-ethylenically unsaturated sulfonic acids such as vinylsulfonic acid, styrenesulfonic acid, (meth)allylsulfonic acid; (meth)acrylamide t-butylsulfonic acid, 2-(meth)acrylamide- 2-methylpropanesulfonic acid, 2-(meth)acrylamido-2-hydroxypropanesulfonic acid, 3-sulfopropane (meth)acrylic acid ester, bis-(3-sulfopropyl) itaconic acid ester and salts thereof, etc. be done.

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

The upper limit of the unsaturated sulfonic acid content 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, etc. The lower limits are exemplified by 60, 50, 40, 30, 20, 10, 5, 1, 0.05, 0.02, 0.01, 0% by mass, and the like. In one embodiment, the content of unsaturated sulfonic acid is preferably 0 to 70% by mass based on 100% by mass of structural units.

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

The content of the acid group-containing monomer such as unsaturated phosphoric acid in 100 mol% of the structural units is not particularly limited, but considering the reaction between the above-described 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, less than 1 mol%, 0 mol%) is preferable with respect to 100 mol% of the structural units.

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, etc., and the lower limit is 50, 40, 30, 20, 10, 5, 1, 0% by mass and the like are exemplified. In one embodiment, the content of the unsaturated phosphoric acid monomer is preferably 0 to 60% by mass relative to 100% by mass of structural units.

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

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

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)acrylates include 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, and decyl (meth)acrylate.

Examples of branched (meth)acrylates include i-propyl (meth)acrylate, i-butyl (meth)acrylate, i-amyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

The alicyclic (meth)acrylic acid ester is exemplified by cyclohexyl (meth)acrylate.

Substituted (meth)acrylates include 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 etc. are illustrated.

The content of the unsaturated carboxylic acid ester in 100 mol% of the structural unit is not particularly limited, but the use of the unsaturated carboxylic acid ester can impart flexibility to the electrode, and is particularly useful for wound and cylindrical batteries. It is useful when it is used, and when manufacturing a separator, it is useful from the viewpoint that the curling of the separator due to the decrease in the glass transition temperature of the component (A) can be suppressed. 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 units is less than 40 mol% (for example, 30, 20, 19, 15, 10 , 5, less than 1 mol %, 0 mol %).

In addition, 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, 80, 70, 60, 50, 40, 30, 20, 19, 15, 10, 5, less than 1% by mass , 0 mass %) is preferred.

α,β-unsaturated nitriles can be preferably used for the purpose of imparting flexibility to electrodes and separators. Examples of α,β-unsaturated nitriles include (meth)acrylonitrile, α-chloro(meth)acrylonitrile, α-ethyl(meth)acrylonitrile, vinylidene cyanide and the like. Among these, (meth)acrylonitrile is preferred, and acrylonitrile is particularly preferred.

The content of α,β-unsaturated nitrile in 100 mol% of structural units is not particularly limited, but less than 40 mol% (for example, 30, 20, 19, 15, 10, 5, 1 mol%) relative to 100 mol% of structural units less than 0 mol %) is preferred. When it is less than 40 mol% relative to 100 mol% of the structural units, 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 α,β-unsaturated nitrile content relative to 100% by mass of the structural unit is exemplified by 60, 50, 40, 30, 20, 10, 5, 1% by mass, etc., and the lower limit is 50, 40, 30% by mass. , 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 structural units is preferably 0 to 60% by mass.

Conjugated dienes include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadiene, substituted and Side chain conjugated hexadiene and the like are exemplified.

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

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

Examples of aromatic vinyl compounds 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 units is not particularly limited, but from the viewpoint of the cycle characteristics of the lithium ion battery, it is preferably less than 10 mol%, more preferably 0 mol%, out of 100 mol% of the structural units. .

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

Acid group-containing monomers such as unsaturated carboxylic acids, unsaturated sulfonic acids, unsaturated phosphoric acids, unsaturated carboxylic acid esters, α,β-unsaturated nitriles, conjugated dienes, and (c) other than aromatic vinyl compounds 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%, and 0.01 per 100 mol% of the constituent units. Less than mol%, 0 mol%, etc. are exemplified, and less than 10% by mass, less than 5% by mass, less than 1% by mass, less than 0.5% by mass, less than 0.1% by mass, relative to 100% by mass of the structural unit, Less than 0.01% by mass, 0% by mass, and the like are exemplified.

The upper limit of the content of 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. 2% by mass, etc., and the lower limits are 95, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 1, 0.5, 0.2, 0.1% by mass, etc. exemplified. In one embodiment, the slurry contains 0.1 to 99.9% by mass of component (A) with respect to 100% by mass.

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

Various known radical polymerization initiators can be used without particular limitation. The radical polymerization initiator is a persulfate such as potassium persulfate and ammonium persulfate; a redox polymerization initiator obtained by combining the above persulfate with a reducing agent such as sodium hydrogen sulfite; 2,2'-azobis-2-amidino Examples include azo initiators such as propane dihydrochloride. The amount of the radical polymerization initiator used is not particularly limited, but is preferably 0.05 to 5.00% by mass, and 0.1 to 3.0% by mass with respect to 100% by mass of the monomer group that provides component (A). more preferred.

Prior to the radical polymerization reaction and/or when water-solubilizing the obtained component (A), for the purpose of improving production stability, common solvents such as ammonia, organic amines, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc. A neutralizing agent may be used to adjust the pH of the reaction solution. In that case, the pH is preferably 2-11. For the same purpose, it is also possible to use EDTA or a salt thereof, which is a metal ion sealant.

When the component (A) has an acid group, it can be used by appropriately adjusting the neutralization rate depending on the application. Here, a neutralization rate of 100% indicates neutralization with the same molar number of alkali as the acid component contained in component (A). A neutralization rate of 50% indicates that half the number of moles of the acid component contained in component (A) was neutralized with alkali. Although the neutralization rate is not particularly limited, the neutralization rate is preferably 70 to 120%, more preferably 80 to 120%, after forming the coating layer or the like. By setting the degree of neutralization after the production of the coating layer to the above range, most of the acid is neutralized, which is preferable because it does not bind with Li ions and the like in the battery to cause a decrease in capacity. Examples of neutralized salts include Li salts, Na salts, K salts, ammonium salts, Mg salts, Ca salts, Zn salts, Al salts and the like.

<Physical properties of component (A)>
The weight average molecular weight (Mw) of 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. are exemplified, The lower limit is 5.5 million, 5 million, 4.5 million, 4 million, 3.5 million, 3 million, 2.9 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 and the like are exemplified. In one embodiment, the weight average molecular weight (Mw) of component (A) is preferably 300,000 to 6,000,000, more preferably 350,000 to 6,000,000, from the viewpoint of dispersion stability of slurry for lithium ion batteries.

The upper limit of the number average molecular weight (Mn) of 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, 850,000, 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, 2.9 million, 2.5 million, 2 million, 1.5 million, 1 million, 950,000, 900,000, 850,000, 800,000, 750,000 . In one embodiment, the number average molecular weight (Mn) of component (A) is preferably 10,000 or more.

The weight-average molecular weight and number-average molecular weight can be determined, for example, as polyacrylic acid conversion values measured under an appropriate solvent by gel permeation chromatography (GPC).

The B-type viscosity of component (A) is not particularly limited, but its upper limit is 8000, 7000, 6000, 5000, 4000, 3000, 2000 mPa s, etc. are exemplified, and the lower limits are 90,000, 80,000, 70,000, 60,000, 50,000, 40,000, 30,000, 20,000, 10,000, 9000, 8000, 7000, 6000, 5000, 4000, 3000, 2000, 1000 mPa·s and the like are exemplified. In one embodiment, the B-type viscosity of component (A) is preferably in the range of 1,000 to 100,000 mPa·s. The B-type viscosity is measured by a B-type viscometer such as "B-type viscometer model BM" manufactured by Toki Sangyo Co., Ltd.

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

The gel fraction is defined by the following formula: gel fraction (%) = {residual insoluble matter in solution (g) / mass of solid content in solution (g)} x 100
It is a value calculated by

<Water-soluble cross-linking agent (A1): Also referred to as (A1) component)
The water-soluble cross-linking agent (A1) of the present invention is an amide group (-C ( =O) NHR-) having a functional group excellent in thermal cross-linking reaction and having the potential to exist stably without cross-linking at room temperature is preferred. In other words, the water-soluble cross-linking agent (A1) in the slurry state stably exists without cross-linking with the water-soluble poly(meth)acrylamide (A), and when the slurry layer (coating layer) after slurry application is dried, Alternatively, it serves to thermally crosslink the water-soluble poly(meth)acrylamide (A) in hot press. In addition, the above is just one theory, and the present invention is not intended to be bound by the above theory.

In one embodiment, the water-soluble cross-linking agent (A1) is selected from at least one selected from the group consisting of formaldehyde, glyoxal, hexamethylenetetramine, urea-formaldehyde resin, and methylolmelamine resin.

The content of the water-soluble cross-linking agent (A1) relative to the water-soluble poly(meth)acrylamide (A) is not particularly limited. The upper limit of the content of the water-soluble cross-linking 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) 0.01, 0.005% by mass, etc., and the lower limits are 2.9, 2.5, 2, 1, 0.5, 0.1, 0.01, 0.005, 0.001% by mass, etc. are 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 separator manufacturability, and a water-soluble cross-linking agent 0.01 to 2.9% by mass is more preferable from the viewpoint of the effect of addition of (A1) and prevention of formation of agglomerates of electrode active material particles and/or ceramic fine particles.

Examples of water include ultrapure water, pure water, distilled water, ion-exchanged water, and tap water.

<Electrode active material (B): Also referred to as component (B)>
In one embodiment, the lithium ion battery slurry contains an electrode active material (B). The electrode active material is exemplified by 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 absorb and release lithium, and an appropriate material can be selected according to the type of lithium ion battery to be used. The above may be used in combination. Examples of negative electrode active materials include carbon materials, silicon materials, oxides containing lithium atoms, lead compounds, tin compounds, arsenic compounds, antimony compounds, aluminum compounds, and other materials that are alloyed with lithium.

The above carbon materials include graphite (also known as graphite, exemplified by 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.), fullerenes, carbon nanotubes, carbon nanofibers, carbon nanohorns, carbon fibrils, mesocarbon microbeads (MCMB), pitch-based carbon fibers, and the like.

In addition to silicon, silicon oxide, and silicon alloys, the silicon materials include SiC, SiOxCy (0< _x ≦3, 0< _y ≦ ₅ ), _Si3N4 , _Si2N2O , _SiOx ( ₀ <x ≤ 2) silicon oxide composites (for example, materials described in JP-A-2004-185810 and JP-A-2005-259697), JP-A-2004-185810 described A silicon material or the like is exemplified. Silicon materials described in Japanese Patent No. 5390336 and Japanese Patent No. 5903761 may also be used.

The silicon oxide is preferably a silicon oxide represented by a composition formula of 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. Silicon alloys of these transition metals are preferred because they have high electronic conductivity and high strength. Silicon alloys are more preferably silicon-nickel alloys or silicon-titanium alloys, and particularly preferably silicon-titanium alloys. The content of silicon in the silicon alloy is preferably 10 mol % or more, more preferably 20 to 70 mol %, based on 100 mol % of the metal element in the alloy. Note that the silicon material may be monocrystalline, polycrystalline, or amorphous.

Moreover, when using a silicon material as an electrode active material, you may use electrode active materials other than a silicon material together. Such an electrode active material includes the above-described carbon materials; conductive polymers such as polyacene; A _X B _Y O _Z (A is an alkali metal or transition metal; 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, 1.5<Z<5. is a number in the range of 00.) and other metal oxides. When a silicon material is used as the electrode active material, it is preferable to use a carbon material together because the volume change associated with the absorption and release of lithium is small.

The above oxides containing lithium atoms include ternary nickel-cobalt lithium manganate, lithium-manganese composite oxides (LiMn ₂ O ₄ etc.), lithium-nickel composite oxides (LiNiO ₂ etc.), lithium-cobalt composite oxides. (LiCoO2, etc.), lithium-iron composite oxides ( _LiFeO2 , etc.), lithium _- nickel-manganese composite _oxides ( _{LiNi0.5Mn0.5O2} , etc.), lithium _- nickel-cobalt composite oxides (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 electrode active materials are exemplified.

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

Positive electrode active materials are roughly classified into active materials containing inorganic compounds and active materials containing organic compounds. Examples of inorganic compounds 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 metals 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 _3O2 , Li[ _{Li0.1Al0.1Mn1.9} ] _O4 and _LiFeVO4 ; Transition metal _sulfides such as _{TiS2 , TiS3} and amorphous _MoS2 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 and V ₆ O ₁₃ ; These compounds may be partially elementally 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 with poor electrical conductivity may be used as an electrode active material covered with a carbon material by allowing a carbon source material to exist during reduction firing. Also, 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/ 3Mn1 / 3O2} , Li[ _{Li0.1Al0.1Mn1.9 ] O4} are _preferred .

The shape of the electrode active material is not particularly limited, and may be any shape such as fine particles or thin film, but fine particles are preferred. The average particle size 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 0.5, 0.1 μm, etc., and the lower limits are 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2.9, 2, 1, 0.5, 0.5 μm, etc. 1 μm and the like are exemplified. In one embodiment, from the viewpoint of forming a uniform and thin coating film, more specifically, if it is 0.1 μm or more, it is easy to handle, and if it is 50 μm or less, it is easy to apply the electrode. The average particle size of the electrode active material is preferably 0.1-50 μm, more preferably 0.1-45 μm, even more preferably 1-10 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 contour line of the particle (the same shall apply hereinafter). In the present disclosure, unless otherwise specified, the "average particle size" refers to particles observed in several to several tens of fields using observation means such as scanning electron microscope (SEM) and transmission electron microscope (TEM). The value calculated as the average particle size of is adopted (the same applies hereinafter).

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

In one embodiment, the content of silicon or silicon oxide in the electrode active material is 20% by mass or more (e.g., 30% by mass or more, 40% by mass, or % by mass, 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, 100% by mass).

In one embodiment, a conductive aid may be included in the slurry. Conductive agents include fibrous carbon such as vapor-grown carbon fiber (VGCF), carbon nanotube (CNT), carbon nanofiber (CNF), graphite particles, carbon black such as acetylene black, ketjen black, furnace black, average Fine powders of Cu, Ni, Al, Si or alloys thereof having a particle size of 10 μm or less are exemplified. The content of the conductive aid is not particularly limited, but is preferably 0 to 10% by mass, more preferably 0.5 to 6% by mass, based on the electrode active material component.

<Ceramic fine particles (C): Also referred to as component (C)>
In one embodiment, the lithium ion battery slurry contains ceramic fine particles (C). The ceramic fine particles are a component that is coated on the active material side of the porous polyolefin resin base material, the plastic nonwoven fabric, and the electrode material, and the gaps between the ceramic fine particles can form pores. Since the ceramic particulates are non-conductive, they can be made insulating, thus preventing short circuits in lithium-ion batteries. In addition, since ceramic fine particles usually have high rigidity, they can increase the mechanical strength of the lithium-ion battery separator. Therefore, even when heat causes shrinkage stress in the porous polyolefin resin base material and plastic non-woven fabric, the lithium-ion battery separator can withstand the stress. As a result, it is possible to prevent the occurrence of short circuits due to shrinkage of the porous polyolefin resin substrate and plastic nonwoven fabric.

By using the ceramic fine particles, the dispersion stability in water is excellent, the slurry for lithium ion batteries is less likely to settle, and a uniform slurry state can be maintained for a long period of time. Also, the use of ceramic fine particles can increase the heat resistance. The ceramic fine particles may be used singly or in combination of two or more.

The material of the ceramic fine particles is preferably an electrochemically stable material. From this point of view, ceramic fine particles are exemplified by oxide particles, nitride particles, covalent crystal particles, poorly soluble ion crystal particles, clay fine particles and the like.
Oxide particles include aluminum oxide (alumina), aluminum oxide hydrates (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 oxides.
Nitride particles are exemplified by aluminum nitride, silicon nitride, boron nitride and the like.
Covalent crystal particles are exemplified by silicon, diamond and the like.
Poorly soluble ionic crystal particles are exemplified by barium sulfate, calcium fluoride, barium fluoride and the like.
Clay fine particles are exemplified by silica, talc, montmorillonite and other clay fine particles.
Among these, boehmite, alumina, magnesium oxide and barium sulfate are preferable, and boehmite is more preferable, from the viewpoint of low water absorption and excellent heat resistance.

The upper limit of the average particle size of the ceramic fine particles is 30, 25, 20, 15, 10, 5, 1, 0.5, 0.1, 0.05 μm, etc., and the lower limit is 25, 20, 15, 10 μm. , 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 Examples include 0.2% by mass, and the lower limits are 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, the slurry contains 0.1 to 99.9% by mass of ceramic fine particles (C) with respect to 100% by mass.

The upper limit of the content of component (A) relative to 100% by mass of 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, etc., and the lower limit is exemplified by 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.5, 1% by mass, etc. be done. In one embodiment, the content of component (A) relative to 100% by mass of ceramic fine particles (C) is preferably 1 to 15% by mass, more preferably 1.5 to 14% by mass, and further 2 to 12% by mass. preferable. With such a content, it is possible to manufacture a lithium-ion battery separator having excellent adhesion, low resistance, and excellent charge-discharge characteristics.

<Slurry viscosity adjusting solvent>
The slurry viscosity adjusting solvent may include, but is not limited to, non-aqueous media having a normal boiling point of 80-350°C. The slurry viscosity adjusting solvent may be used alone or in combination of two or more. Slurry viscosity adjusting solvents include amide solvents such as N-methylpyrrolidone, dimethylformamide and N,N-dimethylacetamide; hydrocarbon solvents such as toluene, xylene, n-dodecane and tetralin; methanol, ethanol, 2-propanol and isopropyl alcohol. , 2-ethyl-1-hexanol, 1-nonanol, alcohol solvents such as lauryl alcohol; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, holone, acetophenone, isophorone; ether solvents such as dioxane, tetrahydrofuran (THF); benzyl acetate, ester solvents such as isopentyl butyrate, methyl lactate, ethyl lactate, and butyl lactate; amine solvents such as o-toluidine, m-toluidine and p-toluidine; lactones such as γ-butyrolactone and δ-butyrolactone; sulfoxides such as dimethyl sulfoxide and sulfolane Sulfone solvent; water and the like are exemplified. Among these, N-methylpyrrolidone is preferable from the viewpoint of coating workability. The content of the non-aqueous medium is not particularly limited, but is preferably 0 to 10% by mass with respect to 100% by mass of the slurry.

<Additive>
The slurry for the thermally crosslinked lithium ion battery is added with a component that does not fall under any of the (A) component, (A1) component, (B) component, (C) component, water, conductive aid, and slurry viscosity adjusting solvent. as an agent.

Examples of additives include dispersants, leveling agents, antioxidants, thickeners, dispersions (emulsions), cross-linking agents and the like.

The content of the additive is exemplified by 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 (A). .

The content of the additive is exemplified by 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 (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, or 0% by mass with respect to 100% by mass of component (B) or component (C) etc. are exemplified.

The content of the additive is exemplified by 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 slurry aqueous solution.

Dispersants are exemplified by anionic compounds, cationic compounds, nonionic compounds, polymer compounds and the like.

Examples of the leveling agent include surfactants such as alkyl-based surfactants, silicon-based surfactants, fluorine-based surfactants, and metal-based surfactants. By using a surfactant, repelling that occurs during coating can be prevented, and the smoothness of the slurry layer (coating layer) can be improved.

Examples of antioxidants include phenol compounds, hydroquinone compounds, organic phosphorus compounds, sulfur compounds, phenylenediamine compounds, polymer-type phenol compounds, and the like. A polymer-type phenol compound is a polymer having a phenol structure in its molecule. The weight average molecular weight of the polymer-type phenol compound is preferably 200-1000, more preferably 600-700.

Thickeners include cellulosic polymers such as carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, 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 acrylate and vinyl alcohol, maleic anhydride or copolymers of maleic acid or fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, modified poly Examples include acrylic acid, oxidized starch, phosphate starch, casein, various modified starches, acrylonitrile-butadiene copolymer hydrides, and the like.

Dispersions (emulsions) include styrene-butadiene copolymer latex, polystyrene polymer latex, polybutadiene polymer latex, acrylonitrile-butadiene copolymer latex, polyurethane polymer latex, and 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 Polymerized resin emulsion, acrylic resin emulsion, polyethylene, polypropylene, polyethylene terephthalate, polyamide (PA), polyimide (PI), polyamideimide (PAI), aromatic polyamide, alginic acid and its salts, polyvinylidene fluoride (PVDF), polytetrafluoro Ethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE) and the like are exemplified. .

Crosslinking agents include formaldehyde, glyoxal, hexamethylenetetramine, urea formaldehyde resins, methylolmelamine resins, carbodiimide compounds, polyfunctional epoxy compounds, oxazoline compounds, polyfunctional hydrazide compounds, isocyanate compounds, melamine compounds, urea compounds, and mixtures thereof. exemplified.

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

Binders other than component (A) may be used alone or in combination of two or more. ), polymers with unsaturated bonds (styrene-butadiene rubber, isoprene rubber, butadiene rubber, etc.), acrylic acid-based polymers (acrylic acid copolymers, methacrylic acid copolymers), carboxymethylcellulose salts, polyvinyl alcohol copolymers Examples include coalescence, polyvinylpyrrolidone, and the like.

The thermally crosslinked lithium ion battery slurry includes a thermally crosslinked lithium ion battery electrode slurry, a thermally crosslinked lithium ion battery negative electrode slurry, a thermally crosslinked lithium ion battery positive electrode slurry, and a thermally crosslinked lithium ion battery separator slurry. can be used as

[3. Method for producing slurry for lithium ion battery]
The present disclosure provides a method for producing the above slurry for lithium ion batteries, comprising adding the water-soluble cross-linking agent (A1) to an aqueous solution containing water-soluble poly(meth)acrylamide (A). The components (A) and the like described in this item are exemplified by those mentioned above.

In one embodiment, the step of obtaining a slurry solution includes adding and mixing a water-soluble poly(meth)acrylamide (A), a water-soluble cross-linking agent (A1), water, and an electrode active material or ceramic fine particles. include. The method of adding the above-mentioned 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 Mix after mixing (also called post-addition)
and the like, and post-addition is preferable from the viewpoint of stability.

Examples of slurry mixing means include ball mills, sand mills, pigment dispersers, grinders, ultrasonic dispersers, homogenizers, planetary mixers, Hobart mixers, and the like.

[4. Electrodes for lithium-ion batteries]
The present disclosure is for a lithium ion battery having a dried product of the slurry for a lithium ion battery on the surface of the current collector, which is obtained by applying the slurry for a thermally crosslinked lithium ion battery to a current collector and causing a thermal crosslinking reaction. Provide electrodes.

Various known current 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 shape of the current collector is not particularly limited, and examples thereof include a metal foil, a metal cylinder, a metal coil, a metal plate, etc. in the case of a metal material, and a carbon plate, a carbon thin film, a carbon cylinder, etc. in the case of a carbon material. Among them, when the electrode active material is used for the negative electrode, copper foil is preferable as the current collector because it is currently used in industrialized products.

The coating means is not particularly limited, and conventionally known coating devices such as a comma coater, gravure coater, micro gravure coater, die coater, and bar coater are exemplified.

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.

The thickness of the electrode (cured coating film) is not particularly limited, but is preferably 5 to 300 μm, more preferably 10 to 250 μm. By setting the content in the above range, it is possible to easily obtain a sufficient Li intercalation/deintercalation function for a high-density current value.

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

[5. Lithium ion battery separator]
The present disclosure provides a dried slurry for a thermally crosslinked lithium ion battery obtained by applying the slurry for a thermally crosslinked lithium ion battery to a porous polyolefin resin base material or a plastic nonwoven fabric and drying it. polyolefin resin base material or plastic non-woven fabric surface.

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 substrate is preferably a porous membrane with fine pores, which is non-electronically conductive, ionically conductive, and highly resistant 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 resins such as polyolefins and mixtures or copolymers thereof as main components. The porous polyolefin resin base material has excellent coating properties when the polymer layer is obtained through the coating process. It is preferable from the viewpoint of increasing the capacity per volume. In addition, "containing as a main component" means containing more than 50% by mass, preferably 75% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably contains 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 substrate is not particularly limited. The content of the polyolefin resin in the base material 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 70% by mass or more and 100% by mass or less. is more preferred.

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

The polyolefin resin used as the material for the porous polyolefin resin substrate has a low melting point and high strength, and therefore, a resin containing high-density polyethylene as a main component is particularly preferable. Furthermore, from the viewpoint of improving the heat resistance of the polyolefin porous substrate, it is more preferable to use together 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 may be any of isotactic polypropylene, syndiotactic polypropylene and atactic polypropylene.

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

In this case, polyolefin resins other than polypropylene are not limited, and examples include homopolymers or copolymers of olefin hydrocarbons such as ethylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene. are exemplified. Specifically, polyolefin resins other than polypropylene are exemplified by polyethylene, polybutene, ethylene-propylene random copolymers, and the like.

From the viewpoint of shutdown properties 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, and the like. It is preferred to use polyethylene. Among these, polyethylene having a density of 0.93 g/cm ³ or more as measured according to JIS K 7112 is more preferable from the viewpoint of strength.

The porous polyolefin resin substrate may contain fillers and fiber compounds for the purpose of controlling strength, hardness and thermal shrinkage. In addition, for the purpose of improving the adhesion with the adhesive layer and lowering the surface tension with the electrolytic solution to improve the impregnation of the liquid, the surface of the porous polyolefin resin substrate is preliminarily coated with a low-molecular-weight compound or a high-molecular-weight compound. may be coated, treated with electromagnetic rays such as ultraviolet rays, or plasma treated with corona discharge or plasma gas. In particular, it contains polar groups such as carboxylic acid groups, hydroxyl groups, and sulfonic acid groups because it has high impregnability with the electrolytic solution and it is easy to obtain adhesion with the coating layer obtained by applying the slurry to the substrate and drying it. 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. Adjusting the thickness to 2 μm or more is preferable from the viewpoint of improving the mechanical strength. On the other hand, adjusting the film thickness to 100 μm or less is preferable because the volume occupied by the separator in the battery is reduced, which tends to be advantageous in 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, more preferably 1 to 10 μm, from the viewpoint of adhesion to the nonwoven fabric and thickness of the separator.

In one embodiment, the plastic nonwoven fabric preferably has an average pore diameter of 1 to 20 μm, more preferably 3 to 20 μm, 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 during lithium dendrite formation.

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

The non-woven 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. Synthetic fibers having different average fiber diameters and pore diameters from those described above may also be used in combination. From the same point of view, fibers other than synthetic fibers may be used as appropriate. When these fibers (synthetic resin fibers and fibers other than synthetic fibers whose average fiber diameter and average pore diameter are outside the ranges specified in this application) are used together, the content is 30 from the viewpoint of ensuring the strength of the nonwoven fabric. % by mass or less is preferable, 20% by mass or less is more preferable, and 10% by mass or less is even more preferable.

Synthetic resin, which is the material of synthetic resin fiber, includes polyolefin resin, polyester resin, polyvinyl acetate resin, ethylene-vinyl acetate copolymer resin. , polyamide-based resins, acrylic-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, polyvinyl ether-based resins, polyvinylketone-based resins Resin, polyether-based resin, polyvinyl alcohol-based resin, diene-based resin, polyurethane-based resin, phenol-based resin, melamine-based resin, furan-based resin , urea-based resin, aniline-based resin, unsaturated polyester-based resin, alkyd resin, fluorocarbon-based resin, silicone-based resin, polyamide-imide-based resin , polyphenylene sulfide-based resin, polyimide-based resin, polycarbonate-based resin, polyazomethine-based resin, polyesteramide resin, polyetheretherketone-based resin, poly -p-phenylenebenzobisoxazole resin, polybenzimidazole resin, ethylene-vinyl alcohol copolymer resin, and the like are exemplified. Among these resins, polyester-based resins, acrylonitrile-based resins, and polyolefin-based resins are preferable in order to increase adhesion to the ceramic fine particles. Moreover, the heat resistance of the separator can be improved by using a polyester-based resin, an acrylic-based resin, or a polyamide-based resin.

The polyester-based resin includes polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PPT), polyethylene naphthalate, polyPENthalate. Resins such as butylene naphthalate-based, polyethylene isonaphthalate-based, and fully aromatic polyester-based resins are exemplified. Derivatives of these resins can also be used. Among these resins, polyethylene terephthalate-based resins are preferred in order to improve heat resistance, electrolyte resistance, and adhesiveness to ceramic fine particles.

Acrylonitrile-based resins include those composed of 100% acrylonitrile polymers, acrylonitrile-acrylonitrile derivatives such as acrylic acid, methacrylic acid, acrylic acid esters, and (meth)acrylic acid derivatives such as methacrylic acid esters, and copolymers such as vinyl acetate. are exemplified.

Examples of polyolefin resins include polypropylene, polyethylene, polymethylpentene, ethylene-vinyl alcohol copolymers, and olefin copolymers. 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-diphenylether terephthalamide, poly-m-phenylene isophthalamide and other wholly aromatic polyamides, A semi-aromatic polyamide having an aliphatic chain in part of the main chain of the aromatic polyamide is exemplified. The wholly aromatic polyamide may be either para-type or meta-type.

The synthetic resin fiber may be a fiber (single fiber) made of a single resin, or a fiber (composite fiber) made of two or more resins. Composite fibers are exemplified by core-sheath type, eccentric type, side-by-side type, sea-island type, orange type, and multi-bimetal type.

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

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

The method of applying the lithium ion battery slurry to 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 a method of scraping off the coating liquid on the non-coated surface side after a lifting method such as dipping.

The lithium ion battery slurry layer (coating layer) can be formed by cross-linking the lithium ion battery slurry containing the component (A) and the component (C) in the layer (coating layer) of the lithium ion battery slurry. . The cross-linking reaction can proceed, for example, when the slurry for lithium ion batteries is dried. Specific drying methods include drying with warm air, hot air, low humidity air, etc.; vacuum drying; and drying by irradiation with infrared rays, far infrared rays, electron beams, and the like.

The lower limit of the drying temperature 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 compounds from the composition for a porous film. , the upper limit is preferably 90° C. or less, more preferably 80° C. or less, from the viewpoint of suppressing thermal deformation of the substrate.

The lower limit of the drying time is preferably 5 seconds or longer, more preferably 10 seconds or longer, particularly preferably 15 seconds or longer, and the upper limit is preferably 3 minutes or shorter, more preferably 2 minutes or shorter. By setting the drying time to at least the lower limit of the above range, the solvent can be sufficiently removed from the composition for porous film, so that the output characteristics of the battery can be improved. Moreover, the production efficiency can be enhanced by setting the content to be equal to or less than the upper limit.

The method for manufacturing the lithium ion battery separator may include any steps other than those described above. The method for producing the lithium ion battery separator may include a step of pressurizing the lithium ion battery slurry layer (coating layer) by pressing such as mold press and roll press. The pressure treatment can improve the binding properties between the substrate and the layer of the slurry for lithium ion batteries. However, from the viewpoint of keeping the porosity of the layer of the slurry for lithium ion batteries within a preferable range, it is preferable to appropriately control the pressure and pressurization time so as not to excessively increase. Further, the method for manufacturing the lithium ion battery separator may include a step of vacuum drying, drying in a dry room, or the like, in order to remove residual moisture.

[6. Separator/electrode laminate for lithium ion battery]
The present disclosure provides a separator/electrode laminate for a lithium ion battery, which is a dried product of the slurry for a thermally crosslinked lithium ion battery obtained by applying the slurry for a thermally crosslinked lithium ion battery to an electrode and drying the slurry. offer.

Various known electrodes can be used for the electrodes used in manufacturing the lithium ion battery separator/electrode laminate, and the electrodes provided by the present disclosure may be used, or the electrodes provided by the present disclosure may be used. It does not have to be an electrode.

A method for producing a separator/electrode laminate for a lithium ion battery includes steps of coating a current collector with a slurry containing an electrode material such as the slurry for a lithium ion battery, drying, and pressing;
A method including a step of applying the lithium ion battery slurry onto the dried slurry containing the electrode material (that is, onto the electrode active material side rather than the current collector side) and drying the applied slurry is exemplified. The coating method, drying method, conditions, etc. are exemplified by those described above.

[7. Lithium-ion battery]
The present disclosure provides a lithium ion battery including the lithium ion battery electrode described above. The present disclosure also provides a lithium ion battery including the lithium ion battery separator and/or the lithium ion battery separator/electrode laminate. The batteries also include electrolytes and packaging materials, which are not particularly limited.

(Electrolyte)
The electrolytic solution is exemplified by a non-aqueous electrolytic solution in which a supporting electrolyte is dissolved in a non-aqueous solvent. In addition, the non-aqueous electrolytic solution may contain a film-forming agent.

Various known non-aqueous solvents can be used without particular limitation, and may be used alone or in combination of two or more. Non-aqueous solvents include chain carbonate solvents such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate; cyclic carbonate solvents such as ethylene carbonate, propylene carbonate and butylene carbonate; chain ether solvents such as 1,2-dimethoxyethane; Cyclic ether solvents such as 2-methyltetrahydrofuran, sulfolane and 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; are exemplified. Among these, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable.

A lithium salt is used as 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. Supporting electrolytes include _LiPF6 , _LiAsF6 , _LiBF4 , _LiSbF6 , _LiAlCl4 , LiClO4, _CF3SO3Li , _{C4F9SO3Li , CF3COOLi} , _{( CF3CO} ) _{2NLi , (} CF _3SO2 ) _2NLi , _{( C2F5SO2} ) _NLi and the like _are exemplified. Among them, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li, which are easily soluble in a solvent and exhibit a high degree of dissociation, are preferable. Since the lithium ion conductivity increases with the use of a supporting electrolyte having a higher degree of dissociation, 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 include carbonate compounds such as vinylene carbonate, vinylethylene carbonate, vinylethyl carbonate, methylphenyl carbonate, fluoroethylene carbonate and difluoroethylene carbonate; alkene sulfides such as ethylene sulfide and propylene sulfide; 1,3-propanesultone, 1 ,4-butane sultone and other sultone compounds; maleic anhydride, succinic anhydride and other acid anhydrides, and the like. 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 in this order. When the content is 10% by mass or less, the advantages of the film-forming agent, such as suppression of initial irreversible capacity and improvement of low-temperature characteristics and rate characteristics, can be easily obtained.

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 a sheet electrode and a separator are spirally formed, a cylinder type with an inside-out structure in which a pellet electrode and a separator are combined, a coin type in which a pellet electrode and a separator are laminated, and the like. Moreover, by housing the batteries of these forms in an arbitrary exterior case, they can be used in arbitrary shapes such as coin-shaped, cylindrical, and rectangular.

The method for manufacturing the lithium ion battery is not particularly limited, and the battery may be assembled by an appropriate procedure according to the structure of the battery. A method for manufacturing a lithium ion battery is exemplified by the method described in JP-A-2013-089437. A battery can be manufactured by placing a negative electrode on an exterior case, providing an electrolytic solution and a separator thereon, placing a positive electrode so as to face the negative electrode, and fixing them with a gasket and a sealing plate.

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

1. Production of component (A) Production Example 1
A reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube was charged with 1,095 g of ion-exchanged water, 400 g (2.81 mol) of a 50% acrylamide aqueous solution, and 0.22 g (0.0014 mol) of sodium methallylsulfonate. was introduced, nitrogen gas was passed through the reaction system to remove oxygen, and then the temperature was raised to 50°C. 2.0 g of 2,2′-azobis-2-amidinopropane dihydrochloride (product name “NC-32” manufactured by Nippo Chemical Co., Ltd.) and 50 g of deionized water were added thereto, and the temperature was raised to 80° C. for 3 A time reaction was carried out to obtain an aqueous solution containing polyacrylamide.

Production example 2
A reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube was charged with 1,428 g of ion-exchanged water, 400 g (2.81 mol) of a 50% acrylamide aqueous solution, and 63.5 g (0.70 mol) of an 80% aqueous acrylic acid solution. , 0.56 g (0.0035 mol) of sodium methallylsulfonate was added. 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 Nippo Chemical Co., Ltd.) 2.5 g and ion-exchanged water 50 g were added thereto, and the temperature was raised to 80° C. for 3 The reaction was carried out for 0.0 hours to obtain an aqueous solution containing a polyacrylamide-acrylic acid copolymer.

Production Examples 3-11
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.

Comparative production example 1
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 were placed in a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube. , 14 g of a 50% acrylamide aqueous solution, 21 g of acrylamide t-butylsulfonic acid, 576 g of butyl acrylate, and 30 g of N-methylolacrylamide were dropped at 50° C. over 1 hour to carry out polymerization. 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：アクリルアミド（三菱ケミカル株式会社製 「５０％アクリルアミド」）
・ＡＴＢＳ：アクリルアミドｔ－ブチルスルホン酸（東亞合成株式会社製 「ＡＴＢＳ」）
・ＮＭＡＭ：Ｎ－メチロールアクリルアミド（東京化成工業株式会社製）
・ＤＭＡＡ：Ｎ，Ｎ－ジメチルアクリルアミド（東京化成工業株式会社製）
・ＡＡ：アクリル酸（大阪有機化学工業株式会社製 「８０％アクリル酸」）
・ＡＮ：アクリロニトリル（三菱ケミカル株式会社製 「アクリロニトリル」）
・ＨＥＭＡ：メタクリル酸２－ヒドロキシエチル（東京化成工業株式会社製）
・ＢＡ：アクリル酸ブチル（和光純薬工業株式会社製）
・ＳＭＡＳ：メタリルスルホン酸ナトリウム

表中に記載の（Ａ）成分の物性は下記のようにして測定した。

・ AM: Acrylamide ("50% acrylamide" manufactured by Mitsubishi Chemical Corporation)
・ ATBS: acrylamide t-butyl sulfonic acid ("ATBS" manufactured by Toagosei Co., Ltd.)
・ NMAM: N-methylol acrylamide (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 (manufactured by Wako Pure Chemical Industries, Ltd.)
・SMAS: Sodium methallyl sulfonate

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

B-type Viscosity The viscosity of each aqueous binder solution was measured at 25° C. under the following conditions using a B-type viscometer (product name “B-type viscometer model BM” manufactured by Toki Sangyo Co., Ltd.).
When the viscosity is 100,000 to 20,000 mPa·s: No. When 4 rotors are used, the rotation speed is 6 rpm, and the viscosity is less than 20,000 mPa·s: No. 3 rotors, 6 rpm.

Weight-Average Molecular Weight The weight-average molecular weight was obtained as a value converted to polyacrylic acid measured under 0.2M phosphate buffer/acetonitrile solution (90/10, pH 8.0) by gel permeation chromatography (GPC). HLC-8220 (manufactured by Tosoh Corporation) was used as the GPC apparatus, and SB-806M-HQ (manufactured by SHODEX) was used as the column.

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% formaldehyde aqueous solution (hereinafter also referred to as formalin) was added in terms of solid content, and the mixture was stirred at 25°C to 0.00% by mass. 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 obtained by blending a water-soluble poly(meth)acrylamide (A) with a water-soluble cross-linking agent (A1) was dried at 120° C. for 4 hours in a circulating air dryer to obtain a solid resin. The mass of the solid resin was accurately measured, immersed in water under conditions of stirring for 3 hours, and then filtered under reduced pressure with a Kiriyama funnel filter paper (No. 50B manufactured by Kiriyama Seisakusho Co., Ltd.). Then, after drying the filtrate at 120° C. for 3 hours, 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 equation.
Gel fraction (%) = {insoluble residue (g) / mass of solid resin (g)} x 100

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

・ホルマリン：３７％ホルムアルデヒド水溶液
・グリオキサール：４０％グリオキサール溶液（和光純薬工業株式会社製）
・ヘキサメチレンテトラミン（和光純薬工業株式会社製）
・メチロールメラミン樹脂
・尿素ホルムアルデヒド樹脂

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

Example 1-1: Evaluation of electrode (1) Production of slurry for lithium ion battery electrode Using a commercially available rotation-revolution mixer (product name “Awatori Mixer”, manufactured by Thinky Co., Ltd.), a container dedicated to the mixer was used. 7 parts by mass of a binder aqueous solution containing the poly(meth)acrylamide (A) and the water-soluble cross-linking agent (A1) obtained in Formulation Example 1 in terms of solid content, and 50 parts by mass of silicon particles having a D50 of 5 μm, 50 parts by mass of natural graphite (product name “Z-5F” manufactured by Ito Graphite Industry Co., Ltd.) was mixed. Ion-exchanged water was added thereto so that the solid content concentration was 40%, and the container was set in the mixer. After kneading at 2000 rpm for 10 minutes, defoaming was performed for 1 minute to obtain a slurry for electrodes.

(2) Manufacture of lithium ion battery electrode On the surface of a current collector made of copper foil, the lithium ion battery slurry is uniformly applied by a doctor blade method so that the film thickness after drying is 25 μm. After drying for 30 minutes at 150° C./vacuum, heat treatment was performed for 120 minutes to obtain an electrode. After that, the film (electrode active material layer) was pressed with a roll press machine so that the density of the film (electrode active material layer) was 1.5 g/cm ³ to obtain an electrode.

(3) Production of Lithium Half Cell In a glove box purged with argon, the above electrodes were punched out to a diameter of 16 mm and placed on a bipolar coin cell (manufactured by Hosen Co., Ltd., trade name "HS Flat Cell"). placed. Next, a separator made of a polypropylene porous film punched to a diameter of 24 mm (manufactured by CS TECH CO., LTD, trade name “Selion P2010”) was placed, and 500 μL of an electrolytic solution was injected so as to prevent air from entering. A lithium half cell was assembled by placing a commercially available metallic lithium foil punched into a size of 16 mm and sealing the exterior body of the bipolar coin cell with screws. 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 table below.

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 preparation of the slurry was visually evaluated according to the following criteria.
⊚: Whole is in the form of a homogeneous paste, no liquid separation is observed, and no aggregates are observed.
◯: The whole is a substantially homogeneous paste, and slight liquid separation is observed, but no aggregates are observed.
Δ: A small amount of aggregates and a slightly large amount of liquid separation are observed at the bottom of the container.
x: A large number of clay-like aggregates are observed at the bottom of the container, and a large amount of liquid separation is also observed.

<Evaluation of electrical properties: springback rate and discharge capacity retention rate>
(1) Charge and discharge measurement Put the lithium half cell manufactured above in a constant temperature bath at 25 ° C., start charging at a constant current (0.1 C), and complete charging when the voltage reaches 0.01 V (cutoff ). Then, discharge was started at a constant current (0.1 C), and charge/discharge was repeated 30 times, with discharge being completed (cutoff) when the voltage reached 1.0V.

(2) Springback Rate of Electrode with Repetition of Charging and Discharging After performing 30 cycles of charging and discharging cycle test at room temperature (25° C.), the lithium half cell was disassembled and the thickness of the electrode was measured. The springback ratio of the electrode was obtained by the following formula.
Springback rate = {(electrode thickness after 30 cycles - current collector thickness) / (electrode thickness before charging and discharging - current collector thickness)} x 100-100 (%)

(3) Discharge capacity retention rate The discharge capacity retention rate was obtained from the following formula.
Discharge capacity retention rate = {(Discharge capacity at 30th cycle)/(Discharge capacity at 1st cycle)} x 100 (%)

In the above measurement conditions, "1 C" indicates a current value at which discharge is completed in 1 hour when a cell having a certain electric capacity is discharged at a constant current. For example, "0.1 C" means a current value at which discharge is completed in 10 hours, and "10 C" means a current value at which discharge is completed in 0.1 hour.

As is clear from the table, both the electrode slurries prepared using the aqueous binder solutions of Examples 1-1 to 1-12 and the lithium half-cells prepared from the electrode slurries were evaluated for springback rate and discharge capacity retention rate. Evaluation was good.

The heat shrinkage resistance, powder drop resistance, adhesion, rate resistance and output characteristics of the obtained separator were measured by the following methods.

<Heat shrinkage resistance>
The separators and separator/electrode laminates obtained in Examples and Comparative Examples were cut into squares of width 12 cm×length 12 cm, and a square of 10 cm on each side was drawn inside the square to obtain a test piece. The test piece was heat-treated by placing it in a constant temperature bath at 150° C. and leaving it 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 obtained as the heat shrinkage rate, and the heat resistance was evaluated according to the following criteria. The smaller the heat shrinkage ratio, the better the heat shrinkage resistance of the separator.
○: Area shrinkage rate is less than 1% △: Area shrinkage rate is 1% or more and less than 3% ×: Area shrinkage rate is 3% or more

<Powder-off resistance>
The separators and separator/electrode laminates obtained in Examples and Comparative Examples were cut into 10 cm x 10 cm squares, the mass (X0) was accurately weighed, one side was attached to cardboard and fixed, and the ceramic layer side was covered with cotton cloth. A weight of 900 g with a diameter of 5 cm covered was put on and these were rubbed against each other for 10 minutes at a rotation speed of 50 rpm. After that, the mass (X1) was measured again accurately, and the following formula: powder falling property = {(X0-X1) / X0} × 100
By calculating the powder falling property (% by mass) according to the following criteria, the powder falling resistance of the separator was evaluated.
A: less than 2% by mass of powder removal property B: 2% by mass or more and less than 5% by mass of powder removal property C: 5% by mass or more of powder removal property

<Separator adhesion (peel strength)>
A test piece having a width of 2 cm and a length of 10 cm is cut out from the separators and separator/electrode laminates obtained in Examples and Comparative Examples, and fixed with the coated surface facing up. Next, a 15 mm wide adhesive tape ("CELLOTAPE (registered trademark)" manufactured by Nichiban Co., Ltd.) (defined in JIS Z1522) was attached to the surface of the ceramic layer of the test piece while being pressed, and then subjected to 25°C conditions. Using a tensile tester ("Tensilon RTM-100" manufactured by A&D Co., Ltd.), the stress when the adhesive tape is peeled off from one end of the test piece in the 180 ° direction at a speed of 30 mm / min. was measured. The measurement was performed 5 times, converted to a value per width of 15 mm, and the average value was calculated as the peel strength. The higher the peel strength, the higher the adhesive 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 separate from the separator base material.

<Rate Tolerance, Output Characteristics>
(1) Production of Laminated Lithium Ion Battery A laminated lithium ion battery was produced in the following manner for measuring rate resistance and output characteristics.
(1-1) Production of Negative Electrode Using a commercially available rotation-revolution mixer (product name: "Awatori Mixer", manufactured by Thinky Co., Ltd.), styrene-butadiene rubber (SBR)/carboxymethylcellulose ( CMC) (1/1 mass ratio) aqueous solution was mixed with 2 parts in terms of solid content and 98 parts of natural graphite (product name “Z-5F” manufactured by Ito Graphite Industry Co., Ltd.). Ion-exchanged water was added thereto so that the solid content concentration was 40%, and the container was set in the mixer. After kneading at 2000 rpm for 10 minutes, defoaming was performed for 1 minute to obtain slurry for lithium ion batteries. A slurry for a lithium ion battery was put on a current collector made of copper foil and coated in a film using a doctor blade. A current collector coated with slurry for a lithium ion battery was dried at 80° C. for 20 minutes to volatilize and remove water, and then closely 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 bonded product was heated at 120° C. for 2 hours in a vacuum dryer and cut into a predetermined shape (rectangular shape of 26 mm×31 mm) to obtain a negative electrode having an electrode active material layer with a thickness of 15 μm.

(1-2) Production of positive electrode LiNi _0.5 Co _0.2 Mn _0.3 O ₂ as a positive electrode active material, acetylene black as a conductive aid, and polyvinylidene fluoride (PVDF) as a binder, each 88 parts by mass. . Next, an aluminum foil was prepared as a current collector for the positive electrode, and the lithium ion battery positive electrode slurry was placed on the aluminum foil and coated with a doctor blade to form a film. The aluminum foil coated with the lithium ion battery positive electrode slurry was dried at 80° C. for 20 minutes to volatilize and remove NMP, and then closely 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 bonded product was heated at 120° C. for 6 hours in a vacuum dryer and cut into a predetermined shape (rectangular shape of 25 mm×30 mm) to obtain a positive electrode having a positive electrode active material layer with a thickness of about 45 μm.

(1-3) Production of Laminated Lithium Ion Battery A laminated lithium ion secondary battery was produced using the above negative electrode and positive electrode or the positive electrode obtained in the example. 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. This electrode plate assembly was covered with a pair of laminate films, and after three sides were sealed, an electrolytic solution was injected into the bag-shaped laminate film. As an electrolytic solution, a solution in which LiPF ₆ was dissolved at a concentration of 1 mol/L in a solvent of ethylene carbonate/ethyl methyl carbonate=1/1 (mass ratio) was used. After that, the remaining one side was sealed to obtain a laminate type lithium ion secondary battery in which the four sides were airtightly sealed and the electrode plate group and the electrolytic solution were sealed. In addition, the positive electrode and the negative electrode have tabs that can be electrically connected to the outside, and a part of the tabs extends outside the laminate type lithium ion secondary battery. When the laminate type lithium ion battery manufactured by the above steps was energized, no problem occurred in operation.

(2) Measurement of rate resistance and output characteristics Using the lithium ion secondary battery manufactured above, charge at 2.5 to 4.2 V at 0.1 C at 25 ° C. When the voltage reaches 4.2 V Then, charging was continued at a constant voltage (4.2 V), and charging was completed (cutoff) when the current value reached 0.01C. Then, charging and discharging at 0.1 C to 2.5 V were repeated 5 times, and after the 6th cycle, only discharging was changed to 1 C and charging and discharging were repeated 50 cycles. A value obtained by calculating the ratio of the 1C discharge capacity at the 6th cycle to the charge capacity at the 6th cycle as a percentage was defined as the initial rate maintenance rate. The higher this value, the better the rate tolerance. Furthermore, the ratio of the 1C discharge capacity at the 50th cycle to the 1C discharge capacity at the 5th cycle was calculated as a percentage, and the value was defined as the capacity retention rate. The larger this value, the better the output characteristics.

Example 2-1
(1) Production of slurry for separator 5 parts by mass of the aqueous solution obtained in Formulation Example 1 in terms of solid content and 113 parts by mass of water are stirred and mixed, and 100 parts by mass of boehmite (average particle size 0.8 μm) is added, Dispersion stirring was performed with a homogenizer (T25 digital ULTRA-TURRAX manufactured by IKA) at 15000 rpm for 60 minutes. Further, ion-exchanged water was added to adjust the viscosity to produce a slurry.

(2) Production of separator: Lamination of separator slurry layer (coating layer) A single-layer polyethylene separator substrate (PE substrate) manufactured by a wet method with 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 side of a 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 for the changes shown in the table below.

Example 2-21
In Example 2-5, the slurry liquid is coated on the positive electrode side instead of the separator, and is coated using a gap coater so that the thickness after drying becomes 3.0 μm, and dried to form a positive electrode for a lithium ion battery. Obtained.

Example 2-22
Same as Example 2-5 except that the slurry liquid 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 in the previous Example 2-5. A separator for a lithium ion battery was obtained by the above operation.

Claims (12)

a water-soluble poly(meth)acrylamide (A) containing 50 mol% or more of structural units derived from the N-unsubstituted or monosubstituted (meth)acrylamide group-containing compound (a) based on 100 mol% of the structural units;
A water-soluble cross-linking agent (A1) that is glyoxal , an electrode active material (B) , water, and a slurry for a thermal cross-linking lithium ion battery containing 0 to 5% by mass of an acid based on 100% by mass of the slurry. a water-soluble poly(meth)acrylamide (A) containing 50 mol% or more of structural units derived from the N-unsubstituted or monosubstituted (meth)acrylamide group-containing compound (a) based on 100 mol% of the structural units;
A water-soluble cross-linking agent (A1) that is glyoxal , ceramic fine particles (C) , water, and a slurry for a thermal cross-linking lithium ion battery containing 0 to 5% by mass of an acid based on 100% by mass of the slurry. The water-soluble cross-linking agent (A1) is added to 0 with respect to 100% by mass of structural units derived from the N-unsubstituted or monosubstituted (meth)acrylamide group-containing compound (a) in the water-soluble poly(meth)acrylamide (A). The slurry for a thermally crosslinked lithium ion battery according to claim 1, containing 0.001 to 3.0% by mass. The water-soluble cross-linking agent (A1) is added to 0 with respect to 100% by mass of structural units derived from the N-unsubstituted or monosubstituted (meth)acrylamide group-containing compound (a) in the water-soluble poly(meth)acrylamide (A). The slurry for a thermally crosslinked lithium ion battery according to claim 2 , containing 0.001 to 3.0% by mass. 2. The slurry for a thermally crosslinked lithium ion battery according to claim 1 , wherein said electrode active material (B) contains silicon or silicon oxide in an amount of 10% by mass or more. The slurry for a thermally crosslinked lithium ion battery according to any one of claims 1 to 5 , comprising adding the water-soluble cross-linking agent (A1) to an aqueous solution containing the water-soluble poly(meth)acrylamide (A). manufacturing method. A lithium ion battery electrode obtained by applying the thermally crosslinkable lithium ion battery slurry according to claim 1 or 3 to a current collector and causing a thermal crosslinking reaction. A lithium ion battery comprising the lithium ion battery electrode according to claim 7 . 5. A lithium ion battery separator obtained by applying the thermally crosslinkable lithium ion battery slurry according to claim 2 or 4 to a porous polyolefin resin base material or plastic nonwoven fabric and thermally crosslinking the slurry. The thermally crosslinked lithium ion battery slurry according to claim 2 or 4 ,
A separator/electrode laminate for a lithium ion battery, obtained by coating an electrode material on the active material side and thermally crosslinking the electrode material. A lithium ion battery comprising the lithium ion battery separator according to claim 9 . A lithium ion battery comprising the lithium ion battery separator/electrode laminate according to claim 10 .