JP6191471B2 - Binder composition for lithium ion secondary battery, production method thereof, slurry composition for lithium ion secondary battery, electrode for lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Description

  The present invention relates to a binder composition for a lithium ion secondary battery, a production method thereof, a slurry composition for a lithium ion secondary battery, an electrode for a lithium ion secondary battery, and a lithium ion secondary battery.

  In recent years, portable terminals such as notebook computers, mobile phones, and PDAs (Personal Digital Assistants) have been widely used. Lithium ion secondary batteries are frequently used as secondary batteries used as power sources for these portable terminals. Mobile terminals are required to have more comfortable portability, and are rapidly becoming smaller, thinner, lighter, and higher performance. As a result, mobile terminals are used in various places. In addition, secondary batteries are also required to be smaller, thinner, lighter, and have higher performance, as with mobile terminals.

  In order to improve the performance of secondary batteries, improvement of electrodes, electrolytes, and other battery members has been studied. Of these electrodes, the electrode active material is usually mixed with a liquid composition in which a binder polymer is dispersed or dissolved in a solvent to obtain a slurry composition, and this slurry composition is applied to a current collector. And dried. In an electrode manufactured by such a method, it has been attempted in the past to improve the performance of a secondary battery by devising a binder (for example, Patent Document 1).

JP 2011-108373 A

However, demands on the performance of lithium ion secondary batteries have recently become more and more advanced, and in particular, improvement of cycle characteristics and low-temperature output characteristics is particularly required.
Accordingly, an object of the present invention is to provide a lithium ion secondary battery binder composition capable of providing a lithium ion secondary battery having excellent cycle characteristics and low temperature output characteristics, a method for producing the same, a lithium ion secondary battery having excellent cycle characteristics and low temperature output characteristics. Slurry composition for lithium ion secondary battery capable of providing a battery, lithium ion secondary battery electrode capable of providing a lithium ion secondary battery excellent in cycle characteristics and low temperature output characteristics, and lithium excellent in cycle characteristics and low temperature output characteristics The object is to provide an ion secondary battery.

The present inventor has studied to solve the above-described problems, and in particular, has studied an additive to the binder that enables good application of the slurry. As a result, by adding a sulfosuccinic acid ester or a salt thereof in combination with a water-soluble polymer to the binder composition for a lithium ion secondary battery, it becomes possible to satisfactorily apply the slurry and further have an affinity with the electrolytic solution. As a result, it was found that a lithium ion secondary battery excellent in cycle characteristics and low temperature output characteristics can be realized, and the present invention was completed.
That is, according to the present invention, the following is provided.

（式中、Ｒ^１及びＲ^２のそれぞれは、独立に、Ｎａ、Ｋ、Ｌｉ、ＮＨ_４及び炭素数１〜１２のアルキル基からなる群より選択され、ＸはＮａ、Ｋ、Ｌｉ及びＮＨ_４からなる群より選択される）で表される化合物である、〔１〕〜〔５〕のいずれか１項に記載のリチウムイオン二次電池用バインダー組成物。
〔７〕 前記粒子状重合体と水溶性重合体との量比が、粒子状重合体／水溶性重合体＝９９／１〜５０／５０である〔１〕〜〔６〕のいずれか１項に記載のリチウムイオン二次電池用バインダー組成物。
〔８〕 〔１〕〜〔７〕のいずれか１項に記載のバインダー組成物、及び電極活物質を含むリチウムイオン二次電池用スラリー組成物。
〔９〕 さらに、増粘剤を含む〔８〕に記載のリチウムイオン二次電池用スラリー組成物。
〔１０〕 〔８〕又は〔９〕に記載のリチウムイオン二次電池用スラリー組成物を、集電体上に、塗布し、乾燥してなるリチウムイオン二次電池用電極。
〔１１〕 正極、負極、及び電解液を備え、
前記正極、前記負極、又はこれらの両方が〔１０〕に記載のリチウムイオン二次電池用電極である、リチウムイオン二次電池。
〔１２〕 〔１〕〜〔７〕のいずれか１項に記載のリチウムイオン二次電池用バインダー組成物の製造方法であって、
粒子状重合体、スルホコハク酸エステル又はその塩、及び水を混合し、混合物（１）を得る工程（１）、及び
前記混合物（１）、及び酸基含有単量体単位を２０〜７０重量％含む水溶性重合体を混合し、前記スルホコハク酸エステル又はその塩の含有割合が前記粒子状重合体及び前記水溶性重合体の合計１００重量部に対して０．０１〜１０重量部である混合物（２）を得る工程（２）
を含む、製造方法。 [1] A particulate polymer, a water-soluble polymer, a sulfosuccinic acid ester or a salt thereof, and water,
The water-soluble polymer contains 20 to 70% by weight of acid group-containing monomer units,
The content ratio of the sulfosuccinic acid ester or a salt thereof is 0.01 to 10 parts by weight with respect to 100 parts by weight in total of the particulate polymer and the water-soluble polymer.
A binder composition for a lithium ion secondary battery.
[2] The binder composition for a lithium ion secondary battery according to [1], wherein the water-soluble polymer further contains 0.1 to 30% by weight of a fluorine-containing monomer unit.
[3] The binder composition for a lithium ion secondary battery according to [1] or [2], wherein the 1% aqueous solution viscosity of the water-soluble polymer is 1-1000 mPa · s.
[4] The binder composition for a lithium ion secondary battery according to any one of [1] to [3], wherein the water-soluble polymer further contains 0.1 to 2% by weight of a crosslinkable monomer unit. .
[5] The binder composition for a lithium ion secondary battery according to any one of [1] to [4], wherein the sulfosuccinic acid ester or a salt thereof is a dialkyl sulfosuccinic acid ester or a salt thereof.
[6] The sulfosuccinic acid ester or a salt thereof is represented by the following formula (i):

(In the formula, each of R ¹ and R ² is independently selected from the group consisting of Na, K, Li, NH ₄ and an alkyl group having 1 to 12 carbon atoms, and X is Na, K, Li, and NH _4. The binder composition for a lithium ion secondary battery according to any one of [1] to [5], which is a compound represented by (1) selected from the group consisting of:
[7] The quantity ratio of the particulate polymer to the water-soluble polymer is any one of [1] to [6], wherein the particulate polymer / water-soluble polymer = 99/1 to 50/50. The binder composition for lithium ion secondary batteries as described in 2.
[8] A slurry composition for a lithium ion secondary battery comprising the binder composition according to any one of [1] to [7] and an electrode active material.
[9] The slurry composition for a lithium ion secondary battery according to [8], further including a thickener.
[10] An electrode for a lithium ion secondary battery, wherein the slurry composition for a lithium ion secondary battery according to [8] or [9] is applied on a current collector and dried.
[11] A positive electrode, a negative electrode, and an electrolytic solution are provided.
A lithium ion secondary battery, wherein the positive electrode, the negative electrode, or both of them are electrodes for a lithium ion secondary battery according to [10].
[12] A method for producing a binder composition for a lithium ion secondary battery according to any one of [1] to [7],
A step (1) of obtaining a mixture (1) by mixing a particulate polymer, a sulfosuccinic acid ester or a salt thereof, and water, and 20 to 70% by weight of the mixture (1) and an acid group-containing monomer unit. A water-soluble polymer is mixed, and the content ratio of the sulfosuccinic acid ester or salt thereof is 0.01 to 10 parts by weight with respect to 100 parts by weight in total of the particulate polymer and the water-soluble polymer ( 2) obtaining step (2)
Manufacturing method.

  According to the present invention, it is possible to obtain a binder composition for a lithium ion secondary battery and a slurry composition for a lithium ion secondary battery that can provide an electrode having a good slurry application and a high affinity with an electrolytic solution. . Thereby, a negative electrode for a secondary battery and a secondary battery having excellent characteristics such as low lithium ion deposition on the electrode surface, excellent cycle characteristics, and excellent low-temperature output characteristics even at low temperatures can be obtained.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples described below, and may be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and the equivalents thereof.

  In the following description, the expression (meth) acryl means acryl, methacryl or a combination thereof. For example, (meth) acrylic acid means acrylic acid, methacrylic acid or a combination thereof. (Meth) acrylate means acrylate, methacrylate or a combination thereof. Furthermore, (meth) acrylonitrile means acrylonitrile, methacrylonitrile or a combination thereof.

  Furthermore, that a substance is water-soluble means that an insoluble content is less than 10% by weight when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C. Further, that a certain substance is water-insoluble means that an insoluble content is 90% by weight or more when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C.

[1. Binder composition for lithium ion secondary battery]
The binder composition for a lithium ion secondary battery of the present invention (hereinafter sometimes simply referred to as “binder composition”) includes a particulate polymer, a water-soluble polymer, a sulfosuccinic acid ester or a salt thereof, and water. .

[1.1. Particulate polymer]
The particulate polymer is a polymer particle. By including the particulate polymer, the binding property of the electrode active material layer can be improved, and the strength against mechanical force applied to the electrode during handling such as winding and transportation can be improved. In addition, since it becomes difficult for the electrode active material to fall off the electrode active material layer, the risk of a short circuit or the like due to foreign matter is reduced. Furthermore, since the electrode active material can be stably held in the electrode active material layer, durability such as cycle characteristics and high-temperature storage characteristics can be improved. Moreover, by being particulate, the particulate polymer can be bound to the electrode active material not by a surface but by a point. For this reason, most of the surface of the electrode active material is not covered with the binder, so that the field of exchange of ions between the electrolytic solution and the electrode active material can be widened. Therefore, the output resistance of the lithium ion secondary battery can be improved by reducing the internal resistance.

  Various polymers can be used as the polymer constituting the particulate polymer, but a water-insoluble polymer is usually used. Examples of the polymer that forms the particulate polymer include polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, A polyacrylonitrile derivative or the like may be used.

Furthermore, the soft polymer particles exemplified below may be used as the particulate polymer. That is, as a soft polymer, for example,
(I) Polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, polyacrylonitrile, butyl acrylate / styrene copolymer, butyl acrylate / acrylonitrile copolymer, butyl acrylate / acrylonitrile / glycidyl methacrylate copolymer, etc. An acrylic soft polymer which is a homopolymer of acrylic acid or a methacrylic acid derivative or a copolymer thereof with a monomer copolymerizable therewith;
(Ii) isobutylene-based soft polymers such as polyisobutylene, isobutylene-isoprene rubber, isobutylene-styrene copolymer;
(Iii) Polybutadiene, polyisoprene, butadiene / styrene random copolymer, isoprene / styrene random copolymer, acrylonitrile / butadiene copolymer, acrylonitrile / butadiene / styrene copolymer, butadiene / styrene / block copolymer, styrene・ Diene-based soft polymers such as butadiene, styrene, block copolymers, isoprene, styrene, block copolymers, styrene, isoprene, styrene, block copolymers;
(Iv) silicon-containing soft polymers such as dimethylpolysiloxane, diphenylpolysiloxane, dihydroxypolysiloxane;
(V) Liquid polyethylene, polypropylene, poly-1-butene, ethylene / α-olefin copolymer, propylene / α-olefin copolymer, ethylene / propylene / diene copolymer (EPDM), ethylene / propylene / styrene copolymer Olefinic soft polymers such as polymers;
(Vi) Vinyl-based soft polymers such as polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, vinyl acetate / styrene copolymer;
(Vii) epoxy-based soft polymers such as polyethylene oxide, polypropylene oxide, epichlorohydrin rubber;
(Viii) Fluorine-containing soft polymers such as vinylidene fluoride rubber and tetrafluoroethylene-propylene rubber;
(Ix) Other soft polymers such as natural rubber, polypeptide, protein, polyester thermoplastic elastomer, vinyl chloride thermoplastic elastomer, polyamide thermoplastic elastomer, and the like. Among these, a diene soft polymer and an acrylic soft polymer are preferable. In addition, these soft polymers may have a cross-linked structure or may have a functional group introduced by modification.
Furthermore, one kind of particulate polymer may be used alone, or two or more kinds of particulate polymers may be used in combination at any ratio.

  The weight average molecular weight of the polymer constituting the particulate polymer is preferably 10,000 or more, more preferably 20,000 or more, and preferably 1,000,000 or less, more preferably 500,000 or less. is there. When the weight average molecular weight of the polymer constituting the particulate polymer is in the above range, the strength of the electrode and the dispersibility of the electrode active material are easily improved.

  The glass transition temperature of the particulate polymer is preferably −75 ° C. or higher, more preferably −55 ° C. or higher, particularly preferably −35 ° C. or higher, and preferably 40 ° C. or lower, more preferably 30 ° C. or lower, More preferably, it is 20 degrees C or less, Most preferably, it is 15 degrees C or less. When the glass transition temperature of the particulate polymer is in the above range, characteristics such as flexibility and winding property of the electrode and binding property between the electrode active material layer and the current collector are highly balanced, which is preferable. The glass transition temperature of the particulate polymer can be adjusted by combining various monomers.

  The volume average particle diameter D50 of the particulate polymer is preferably 50 nm or more, more preferably 70 nm or more, and preferably 500 nm or less, more preferably 400 nm or less. When the volume average particle diameter D50 of the particulate polymer is in the above range, the strength and flexibility of the obtained electrode can be improved.

  The production method of the particulate polymer is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method may be used. Among these, the emulsion polymerization method and the suspension polymerization method are preferable because they can be polymerized in water and used as they are as the material of the binder composition of the present invention. Moreover, when manufacturing a particulate polymer, it is preferable to include a dispersing agent in the reaction system. The particulate polymer is usually composed of a polymer substantially constituting it, but may be accompanied by any component such as an additive added during the polymerization.

[1.2. Water-soluble polymer]
The water-soluble polymer usually has an action of uniformly dispersing the electrode active material in the slurry composition containing the binder composition of the present invention. Further, the water-soluble polymer has an action of adjusting the viscosity of the slurry composition and can function as a thickener. Furthermore, the water-soluble polymer acts to bind the electrode active material and the current collector by interposing between the electrode active materials and between the electrode active material and the current collector in the electrode active material layer. Can play. In addition, the water-soluble polymer can form a stable layer that covers the electrode active material in the electrode active material layer, and can exert an action of suppressing decomposition of the electrolytic solution.

[1.2.1. (Acid group-containing monomer unit)
The water-soluble polymer includes an acid group-containing monomer unit. The acid group-containing monomer unit is a structural unit having a structure formed by polymerizing an acid group-containing monomer.

  An acid group refers to a group that exhibits acidity. Examples of acid groups include carboxylic acid groups such as carboxyl groups and carboxylic anhydride groups, sulfonic acid groups, and phosphoric acid groups. Of these, carboxylic acid groups and sulfonic acid groups are preferred.

  Examples of the acid group-containing monomer include an ethylenically unsaturated carboxylic acid monomer, an ethylenically unsaturated sulfonic acid monomer, and an ethylenically unsaturated phosphoric acid monomer.

  Examples of the ethylenically unsaturated carboxylic acid monomer include an ethylenically unsaturated monocarboxylic acid monomer and derivatives thereof, an ethylenically unsaturated dicarboxylic acid monomer and acid anhydrides thereof, and derivatives thereof. Examples of ethylenically unsaturated monocarboxylic acid monomers include acrylic acid, methacrylic acid, and crotonic acid. Examples of derivatives of ethylenically unsaturated monocarboxylic acid monomers include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxy. Acrylic acid and (beta) -diaminoacrylic acid are mentioned. Examples of ethylenically unsaturated dicarboxylic acid monomers include maleic acid, fumaric acid, and itaconic acid. Examples of acid anhydrides of ethylenically unsaturated dicarboxylic acid monomers include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Examples of derivatives of ethylenically unsaturated dicarboxylic acid monomers include substituted maleic acids such as methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid; and diphenyl maleate, Examples thereof include maleyl esters such as nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, fluoroalkyl maleate and methylallyl maleate. Among these, ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid are preferable. This is because the solubility of the obtained water-soluble polymer in water can be further increased.

  Examples of ethylenically unsaturated sulfonic acid monomers include monomers sulfonated one of conjugated double bonds of diene compounds such as isoprene and butadiene, vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, sulfone. Examples include ethyl methacrylate, sulfopropyl methacrylate, sulfobutyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 3-allyloxy-2-hydroxypropanesulfonic acid (HAPS), and salts thereof. Examples of the salt include lithium salt, sodium salt, potassium salt and the like. For example, the sodium salt (NaSS) of styrene sulfonic acid (p-styrene sulfonic acid etc.) can be mentioned. Preferred examples of the ethylenically unsaturated sulfonic acid monomer include AMPS and NaSS. AMPS is particularly preferable.

Examples of the ethylenically unsaturated phosphoric acid monomer include monomers having an ethylenically unsaturated group and a -OP (= O) (-OR ^a ) -OR ^b group (R ^a and R ^b is independently a hydrogen atom or any organic group.) or a salt thereof. Specific examples of the organic group as R ^a and R ^b include an aliphatic group such as an octyl group and an aromatic group such as a phenyl group. Specific examples of the ethylenically unsaturated phosphoric acid monomer include a compound containing a phosphoric acid group and an allyloxy group, and a phosphoric acid group-containing (meth) acrylic acid ester. Examples of the compound containing a phosphoric acid group and an allyloxy group include 3-allyloxy-2-hydroxypropane phosphoric acid. Examples of phosphoric acid group-containing (meth) acrylic acid esters include dioctyl-2-methacryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, monomethyl-2-methacryloyloxyethyl phosphate, dimethyl-2-methacrylate. Leuoxyethyl phosphate, monoethyl-2-methacryloyloxyethyl phosphate, diethyl-2-methacryloyloxyethyl phosphate, monoisopropyl-2-methacryloyloxyethyl phosphate, diisopropyl-2-methacryloyloxyethyl phosphate, mono n-butyl -2-methacryloyloxyethyl phosphate, di-n-butyl-2-methacryloyloxyethyl phosphate, monobutoxyethyl-2-methacryloyloxyethyl phosphate , Dibutoxyethyl-2-methacryloyloxyethyl phosphate, mono (2-ethylhexyl) -2-methacryloyloxyethyl phosphate, and di (2-ethylhexyl) -2-methacryloyloxyethyl phosphate.

Among the above-described examples, preferred are ethylenically unsaturated carboxylic acid monomers and ethylenically unsaturated sulfonic acid monomers, and more preferred are acrylic acid, methacrylic acid, itaconic acid and 2- Acrylamide-2-methylpropanesulfonic acid is mentioned, acrylic acid and methacrylic acid are more preferable, and methacrylic acid is particularly preferable.
As the acid group-containing monomer and the acid group-containing monomer unit, one type may be used alone, or two or more types may be used in combination at any ratio.

  The ratio of the acid group-containing monomer unit in the water-soluble polymer is 20 to 70% by weight. The ratio of the acid group-containing monomer unit in the water-soluble polymer is preferably 25% by weight or more, more preferably 30% by weight or more, and preferably 65% by weight or less, more preferably 60% by weight or less. . When the ratio of the acid group-containing monomer unit is not more than the above upper limit value, the adhesion between the electrode active material layer and the current collector can be enhanced. Moreover, when the ratio of the acid group-containing monomer unit is equal to or higher than the lower limit, precipitation of lithium ions in the electrolytic solution can be reduced, thereby improving the cycle characteristics of the lithium ion secondary battery. . Here, the ratio of the acid group-containing monomer unit in the water-soluble polymer usually corresponds to the ratio (preparation ratio) of the acid group-containing monomer in all the monomers used in the production of the water-soluble polymer.

[1.2.2. (Fluorine-containing monomer unit)
The water-soluble polymer can contain a fluorine-containing monomer unit. The fluorine-containing monomer unit is a structural unit having a structure formed by polymerizing a fluorine-containing monomer.
Examples of the fluorine-containing monomer include fluorine-containing (meth) acrylic acid ester monomers. As a fluorine-containing (meth) acrylic acid ester monomer, the monomer represented by following formula (ii) is mentioned, for example.

In the formula (ii), R ³ represents a hydrogen atom or a methyl group.
In the formula (ii), R ⁴ represents a hydrocarbon group containing a fluorine atom. The carbon number of the hydrocarbon group is usually 1 or more and usually 18 or less. The number of fluorine atoms contained in R ⁴ may be 1 or 2 or more.

  Examples of fluorine-containing (meth) acrylic acid ester monomers represented by formula (ii) include (meth) acrylic acid alkyl fluoride, (meth) acrylic acid fluoride aryl, and (meth) acrylic acid fluoride. Aralkyl is mentioned. Of these, alkyl fluoride (meth) acrylate is preferable. Examples of fluorinated alkyl (meth) acrylates include (meth) acrylic acid perfluoroalkyl esters and other (meth) acrylic acid fluoroalkyl esters. Specific examples of such monomers include 2,2,2-trifluoroethyl (meth) acrylate, β- (perfluorooctyl) ethyl (meth) acrylate, 2,2, (meth) acrylic acid. 3,3-tetrafluoropropyl, (meth) acrylic acid 2,2,3,4,4,4-hexafluorobutyl, (meth) acrylic acid 1H, 1H, 9H-perfluoro-1-nonyl, (meth) 1H, 1H, 11H-perfluoroundecyl acrylate, perfluorooctyl (meth) acrylate, perfluoroethyl (meth) acrylate, trifluoromethyl (meth) acrylate, (meth) acrylic acid 3 [4 [1 -Trifluoromethyl-2,2-bis [bis (trifluoromethyl) fluoromethyl] ethynyloxy] benzooxy] 2-hydroxypropyl and the like It is. Moreover, a fluorine-containing (meth) acrylic acid ester monomer and a fluorine-containing (meth) acrylic acid ester monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Also good.

  The proportion of fluorine-containing monomer units in the water-soluble polymer is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, particularly preferably 0.5% by weight or more, and preferably 30%. % By weight or less, more preferably 25% by weight or less, particularly preferably 20% by weight or less. When the ratio of the fluorine-containing monomer unit is equal to or higher than the lower limit, precipitation of lithium ions in the electrolytic solution can be reduced, thereby improving the cycle characteristics of the lithium ion secondary battery. Here, the ratio of the fluorine-containing monomer unit in the water-soluble polymer usually corresponds to the ratio (preparation ratio) of the fluorine-containing monomer in all monomers used in the production of the water-soluble polymer.

[1.2.3. Crosslinkable monomer unit)
The water-soluble polymer can contain a crosslinkable monomer unit. The crosslinkable monomer unit is a structural unit obtained by polymerizing a crosslinkable monomer. A crosslinkable monomer is a monomer that can form a crosslinked structure during or after polymerization by heating or irradiation with energy rays. By including a crosslinkable monomer unit, the water-soluble polymer can be crosslinked, so that the strength and stability of the electrode active material layer can be increased. In addition, swelling of the electrode active material layer with respect to the electrolytic solution can be suppressed, and the low temperature characteristics of the lithium ion secondary battery can be improved.

  As the crosslinkable monomer, a monomer capable of forming a crosslinked structure upon polymerization can be used. Examples of the crosslinkable monomer include monomers having two or more reactive groups per molecule. More specifically, a monofunctional monomer having a heat-crosslinkable crosslinkable group and one olefinic double bond per molecule, and a polyfunctional having two or more olefinic double bonds per molecule. Ionic monomers.

  Examples of thermally crosslinkable groups contained in the monofunctional monomer include epoxy groups, N-methylolamide groups, oxetanyl groups, oxazoline groups, and combinations thereof. Among these, an epoxy group is more preferable in terms of easy adjustment of crosslinking and crosslinking density.

  Examples of the crosslinkable monomer having an epoxy group as a thermally crosslinkable group and having an olefinic double bond include vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl. Unsaturated glycidyl ethers such as ether; butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene Monoepoxides of dienes or polyenes such as; alkenyl epoxides such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; and glycidyl acrylate, glycidyl methacrylate, Glycidyl crotonate, glycidyl Unsaturated carboxylic acids such as -4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexene carboxylic acid, glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid Glycidyl esters; and the like.

  Examples of the crosslinkable monomer having an N-methylolamide group as a thermally crosslinkable group and having an olefinic double bond have a methylol group such as N-methylol (meth) acrylamide (meta ) Acrylamides.

  Examples of the crosslinkable monomer having an oxetanyl group as a heat crosslinkable group and having an olefinic double bond include 3-((meth) acryloyloxymethyl) oxetane, 3-((meth) Acryloyloxymethyl) -2-trifluoromethyloxetane, 3-((meth) acryloyloxymethyl) -2-phenyloxetane, 2-((meth) acryloyloxymethyl) oxetane, and 2-((meth) acryloyloxymethyl ) -4-trifluoromethyloxetane.

  Examples of the crosslinkable monomer having an oxazoline group as a thermally crosslinkable group and having an olefinic double bond include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2- Oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and And 2-isopropenyl-5-ethyl-2-oxazoline.

  Examples of multifunctional monomers having two or more olefinic double bonds include allyl (meth) acrylate, ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, Tetraethylene glycol di (meth) acrylate, trimethylolpropane-tri (meth) acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane, trimethylolpropane-diallyl Examples include ethers, allyl or vinyl ethers of polyfunctional alcohols other than those described above, triallylamine, methylenebisacrylamide, and divinylbenzene.

Especially, as a crosslinkable monomer, ethylene dimethacrylate, allyl glycidyl ether, and glycidyl methacrylate are preferable, and ethylene dimethacrylate and glycidyl methacrylate are more preferable.
Moreover, a crosslinking | crosslinked monomer and a crosslinking | crosslinked monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In the water-soluble polymer, the proportion of the crosslinkable monomer unit is preferably 0.1% by weight or more, more preferably 0.15% by weight or more, particularly preferably 0.2% by weight or more, and preferably It is 2% by weight or less, more preferably 1.5% by weight or less, and particularly preferably 1.0% by weight or less. When the content ratio of the crosslinkable monomer unit is not less than the lower limit of the above range, the cycle characteristics of the lithium ion secondary battery can be improved and the battery life can be extended. Moreover, the adhesiveness of an electrode active material layer and a collector can be improved because it is below the upper limit of the said range. Usually, the ratio of the crosslinkable monomer unit in the water-soluble polymer coincides with the ratio (charge ratio) of the crosslinkable monomer in all the monomers of the water-soluble polymer.

[1.2.4. Arbitrary structural unit)
The water-soluble polymer may contain an arbitrary structural unit in addition to the units described above.

  For example, the water-soluble polymer can include a hydroxyl group-containing monomer unit. A hydroxyl group-containing monomer unit is a structural unit having a structure formed by polymerizing a hydroxyl group-containing monomer. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate, 2-hydroxy methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, and 3-chloro-2-hydroxypropyl methacrylate. Hydroxyalkyl acrylates such as di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, and 2-hydroxyethyl methyl fumarate; Examples include alcohols, monoallyl ethers of polyhydric alcohols, and vinyl alcohol. Of these, hydroxyalkyl acrylate is preferable, and 2-hydroxyethyl acrylate is particularly preferable. Moreover, a hydroxyl-containing monomer and a hydroxyl-containing monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The proportion of the hydroxyl group-containing monomer unit in the water-soluble polymer is preferably 0.5% by weight or more, more preferably 1% by weight or more, still more preferably 1.5% by weight or more, and preferably 10% by weight. % Or less, more preferably 8% by weight or less, and even more preferably 5% by weight or less. When the ratio of the hydroxyl group-containing monomer unit is not less than the lower limit, the dispersibility of the particles such as the electrode active material and the particulate polymer can be increased in the slurry composition containing the binder composition of the present invention. Moreover, when the ratio of the hydroxyl group-containing monomer unit is not more than the above upper limit value, the cycle characteristics of the lithium ion secondary battery can be improved and the battery life can be extended. Here, the ratio of the hydroxyl group-containing monomer unit in the water-soluble polymer usually corresponds to the ratio (preparation ratio) of the hydroxyl group-containing monomer in all monomers used for the production of the water-soluble polymer.

  In addition, for example, the water-soluble polymer may contain (meth) acrylate monomer units other than the fluorine-containing (meth) acrylate monomer units. The (meth) acrylic acid ester monomer unit is a structural unit having a structure formed by polymerizing a (meth) acrylic acid ester monomer. However, among the (meth) acrylate monomers, those containing fluorine are distinguished from (meth) acrylate monomers as fluorine-containing (meth) acrylate monomers. Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, Acrylic acid alkyl esters such as 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; and methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t -Butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl Methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n- tetradecyl methacrylate, methacrylic acid alkyl esters such as stearyl methacrylate. Moreover, a (meth) acrylic acid ester monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In the water-soluble polymer, the proportion of the (meth) acrylic acid ester monomer unit is preferably 25% by weight or more, more preferably 30% by weight or more, particularly preferably 35% by weight or more, and preferably 75% by weight. % Or less, more preferably 70% by weight or less, and particularly preferably 65% by weight or less. When the amount of the (meth) acrylic acid ester monomer unit is not less than the lower limit of the above range, the adhesion of the electrode active material layer to the current collector can be increased. Moreover, the softness | flexibility of an electrode can be improved because it is below the upper limit of the said range. Here, the ratio of the (meth) acrylic acid ester monomer unit in the water-soluble polymer is usually the ratio of the (meth) acrylic acid ester monomer in all the monomers of the water-soluble polymer (preparation ratio). Match.

  Also, for example, the water-soluble polymer can contain reactive surfactant units. The reactive surfactant unit is a structural unit obtained by polymerizing a reactive surfactant. The reactive surfactant unit forms part of the water-soluble polymer and can function as a surfactant.

  The reactive surfactant is a monomer having a polymerizable group that can be copolymerized with another monomer and having a surfactant group (hydrophilic group and hydrophobic group). Usually, the reactive surfactant has a polymerizable unsaturated group, and this group also acts as a hydrophobic group after polymerization. Examples of the polymerizable unsaturated group that the reactive surfactant has include a vinyl group, an allyl group, a vinylidene group, a propenyl group, an isopropenyl group, and an isobutylidene group. One kind of the polymerizable unsaturated group may be used alone, or two or more kinds may be used in combination at any ratio.

  The reactive surfactant usually has a hydrophilic group as a portion that exhibits hydrophilicity. Reactive surfactants are classified into anionic, cationic and nonionic surfactants depending on the type of hydrophilic group.

Examples of the anionic hydrophilic group include —SO ₃ M, —COOM, and —PO (OM) ₂ . Here, M represents a hydrogen atom or a cation. Examples of cations include alkali metal ions such as lithium, sodium and potassium; alkaline earth metal ions such as calcium and magnesium; ammonium ions; ammonium ions of alkylamines such as monomethylamine, dimethylamine, monoethylamine and triethylamine; and And ammonium ions of alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine.
Examples of cationic hydrophilic groups include primary amine salts such as —NH ₂ HX, secondary amine salts such as —NHCH ₃ HX, tertiary amine salts such as —N (CH ₃ ) ₂ HX, Quaternary amine salts such as —N ⁺ (CH ₃ ) ₃ X ^— and the like can be mentioned. Here, X represents a halogen group.
-OH is mentioned as an example of a nonionic hydrophilic group.

  Examples of suitable reactive surfactants include compounds represented by the following formula (iii).

In the formula (iii), R represents a divalent linking group. Examples of R include -Si-O- group, methylene group and phenylene group.
In the formula (iii), R ⁵ represents a hydrophilic group. An example of R ³ includes —SO ₃ NH ₄ .
In formula (iii), n represents an integer of 1 to 100.

Another example of a suitable reactive surfactant has a structural unit having a structure formed by polymerizing ethylene oxide and a structural unit having a structure formed by polymerizing butylene oxide. Examples thereof include compounds having an alkenyl group having a terminal double bond and —SO ₃ NH ₄ (for example, trade names “Latemul PD-104” and “Latemul PD-105”, manufactured by Kao Corporation).
A reactive surfactant may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In the water-soluble polymer, the content of the reactive surfactant unit is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and particularly preferably 0.5% by weight or more. Is 5% by weight or less, more preferably 4% by weight or less, and particularly preferably 2% by weight or less. By making the content rate of a reactive surfactant unit more than the lower limit of the said range, the dispersibility of the slurry composition containing the binder composition of this invention can be improved. Moreover, durability of an electrode can be improved by setting it as below an upper limit.

  A further example of an arbitrary structural unit that the water-soluble polymer may have includes a structural unit having a structure formed by polymerizing the following monomers. That is, aromatic vinyl monomers such as styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, α-methyl styrene, divinyl benzene, etc. Amide monomers such as acrylamide; α, β-unsaturated nitrile compound monomers such as acrylonitrile and methacrylonitrile; olefin monomers such as ethylene and propylene; halogen atoms such as vinyl chloride and vinylidene chloride Monomers; vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate; vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; methyl vinyl ketone, ethyl vinyl ketone, Butyl vinyl It is formed by polymerizing one or more of vinyl ketone monomers such as ketone, hexyl vinyl ketone and isopropenyl vinyl ketone; and heterocyclic ring-containing vinyl compound monomers such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole. Examples include structural units having a structure.

[1.2.5. Properties of water-soluble polymer)
The viscosity of a 1% by weight aqueous solution of the water-soluble polymer is preferably 1 mPa · s or more, more preferably 2 mPa · s or more, particularly preferably 5 mPa · s or more, and preferably 1000 mPa · s or less, more preferably 500 mPa · s. · S or less, particularly preferably 100 mPa · s or less. By setting the viscosity to the lower limit value or more, the adhesion strength between the current collector and the electrode active material layer can be improved. The viscosity can be adjusted by, for example, the molecular weight of the water-soluble polymer. Here, the said viscosity is a value when it measures at 25 degreeC and rotation speed 60rpm using a B-type viscometer.

The weight average molecular weight of the water-soluble polymer is preferably 500 or more, more preferably 700 or more, particularly preferably 1000 or more, and preferably 500,000 or less, more preferably 450,000 or less, and particularly preferably 400,000 or less. By setting the weight average molecular weight of the water-soluble polymer to be equal to or higher than the lower limit of the above range, the strength of the water-soluble polymer can be increased and the durability of the electrode can be improved. Moreover, the adhesive strength with the adhesiveness of a collector and an electrode active material layer can be improved by setting it as below an upper limit.
Here, the weight average molecular weight of the water-soluble polymer is polystyrene using gel permeation chromatography (GPC) as a developing solvent, a solution obtained by dissolving 0.85 g / ml sodium nitrate in a 10% by volume aqueous solution of dimethylformamide. It can be obtained as a conversion value.

[1.2.6. Method for producing water-soluble polymer]
The water-soluble polymer can be produced, for example, by polymerizing a monomer composition containing the above-described monomer in an aqueous solvent. At this time, the ratio of each monomer in the monomer composition is usually the same as the ratio of structural units in the water-soluble polymer.

The aqueous solvent is not particularly limited as long as the water-soluble polymer can be dispersed. Usually, the boiling point at normal pressure is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and preferably 350 ° C. or lower, more preferably 300 ° C. or lower. Examples of the aqueous solvent will be given below. In the following examples, the number in parentheses after the solvent name is the boiling point (unit: ° C) at normal pressure, and the value after the decimal point is a value rounded off or rounded down.
Examples of aqueous solvents include water (100); ketones such as diacetone alcohol (169) and γ-butyrolactone (204); ethyl alcohol (78), isopropyl alcohol (82), normal propyl alcohol (97) and the like. Alcohols: propylene glycol monomethyl ether (120), methyl cellosolve (124), ethyl cellosolve (136), ethylene glycol tertiary butyl ether (152), butyl cellosolve (171), 3-methoxy-3-methyl-1-butanol (174) ), Ethylene glycol monopropyl ether (150), diethylene glycol monobutyl ether (230), triethylene glycol monobutyl ether (271), dipropylene glycol monomethyl ether (188) Glycol ethers; and 1,3-dioxolane (75), 1,4-dioxolane (101), ethers such as tetrahydrofuran (66 the like). Among these, water is particularly preferable from the viewpoint that it is not flammable and a polymer dispersion can be easily obtained. Further, water may be used as the main solvent, and an aqueous solvent other than the above-described water may be mixed and used within a range in which the dispersion state of the polymer can be secured.

  The polymerization method is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used. As the polymerization method, any method such as ion polymerization, radical polymerization, and living radical polymerization can be used. Among them, the emulsion polymerization method is particularly preferable from the viewpoint of production efficiency. For example, when an emulsion polymerization method is employed, a high molecular weight body is easily obtained. Further, for example, when the emulsion polymerization method is employed, the polymer is obtained in the state of being dispersed in water as it is, so that the redispersion treatment is unnecessary, and it can be directly used for the production of the slurry composition of the present invention.

  The emulsion polymerization method is usually performed by a conventional method. For example, the method is described in “Experimental Chemistry Course” Vol. 28, (Publisher: Maruzen Co., Ltd., edited by The Chemical Society of Japan). That is, water, an additive such as a dispersant, an emulsifier, a crosslinking agent, a polymerization initiator, and a monomer are added to a sealed container equipped with a stirrer and a heating device so as to have a predetermined composition, and the composition in the container This is a method in which a product is stirred to emulsify monomers and the like in water, and the temperature is increased while stirring to initiate polymerization. Alternatively, emulsion polymerization can be carried out by emulsifying the above composition and then placing it in a closed container and similarly starting the reaction.

  Examples of polymerization initiators include organic compounds such as lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 3,3,5-trimethylhexanoyl peroxide, and the like. Peroxides; azo compounds such as α, α′-azobisisobutyronitrile; ammonium persulfate; and potassium persulfate. A polymerization initiator may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  An emulsifier, a dispersant, a polymerization initiator, and the like are generally used in these polymerization methods, and the amount used is usually an amount generally used.

The polymerization temperature and polymerization time can be arbitrarily selected depending on the polymerization method and the type of polymerization initiator. Usually, the polymerization temperature is about 30 ° C. or more, and the polymerization time is about 0.5 to 30 hours.
Further, additives such as amines may be used as a polymerization aid.

  A reaction solution containing a water-soluble polymer is usually obtained by polymerization. The obtained reaction solution is usually acidic, and the water-soluble polymer is often dispersed in an aqueous solvent. The water-soluble polymer dispersed in the water-soluble solvent as described above can be usually made soluble in an aqueous solvent by adjusting the pH of the reaction solution to, for example, 7 to 13. You may take out a water-soluble polymer from the reaction liquid obtained in this way. However, usually, water is used as an aqueous medium, and the binder composition of the present invention is produced using a water-soluble polymer dissolved in water.

  The solution containing a water-soluble polymer in an aqueous solvent is usually acidic. Therefore, it may be alkalized to pH 7 to pH 13 as necessary. Thereby, the handleability of a solution can be improved and the applicability | paintability of the slurry composition of this invention can be improved. Examples of the method for alkalinizing to pH 7 to pH 13 include alkaline metal aqueous solutions such as lithium hydroxide aqueous solution, sodium hydroxide aqueous solution and potassium hydroxide aqueous solution; alkaline earth metal aqueous solutions such as calcium hydroxide aqueous solution and magnesium hydroxide aqueous solution; The method of mixing aqueous alkali solution, such as aqueous ammonia solution, is mentioned. One kind of the alkaline aqueous solution may be used alone, or two or more kinds may be used in combination at any ratio.

[1.2.7. Amount of water-soluble polymer]
The amount ratio of the particulate polymer to the water-soluble polymer is preferably particulate polymer / water-soluble polymer = 99/1 to 50/50, more preferably 98/2 to 60/40. Preferably, 97/3 to 70/30 is even more preferable. By setting it as the said range, coexistence of adhesiveness and a lifetime characteristic can be aimed at.

[1.3. Sulfosuccinic acid ester or salt thereof]
The binder composition of the present invention contains a sulfosuccinic acid ester or a salt thereof. By including the sulfosuccinic acid ester or a salt thereof, the ease of application of the slurry composition containing the binder composition is greatly improved, and a homogeneous slurry layer can be obtained. As a result, the low-temperature acceptance characteristics of the electrode, the low-temperature output characteristics, and the cycle characteristics of the battery are improved.

  The sulfosuccinic acid ester is a monoester, diester or triester of sulfosuccinic acid, preferably a monoester or a diester, and more preferably a diester. The sulfosuccinic acid ester is preferably a mono-, di- or trialkyl ester, more preferably a monoalkyl ester or a dialkyl ester, and even more preferably a dialkyl ester.

  The sulfosuccinic acid ester or a salt thereof is preferably a compound represented by the following formula (i).

In formula (i), each of R ¹ and R ² is independently selected from the group consisting of Na, K, Li, NH ₄ and an alkyl group having 1 to 12 carbon atoms, and X is Na, K, Li and Selected from the group consisting of NH ₄ . When each of R ¹ and R ² is an alkyl group, the carbon number thereof is more preferably 1 to 12, and even more preferably 2 to 10. When each of R ¹ and R ² is an alkyl group, it may be a linear alkyl group, a branched alkyl group, or an alkyl group having an alicyclic structure. Also good. Preferable examples of such an alkyl group include octyl group, cyclohexyl group, and amyl group. Among these, an octyl group, a cyclohexyl group, and an amyl group are particularly preferable.

In formula (i), X is preferably selected from the group consisting of Na, Li and NH ₄ , more preferably from the group consisting of Na and Li. In addition, when each of R ¹ and R ² is other than an alkyl group, these are also preferably selected from the group consisting of Na and Li. When each of R ¹ and R ² is other than an alkyl group, these are usually the same as X.

  More specific examples of the compound represented by the formula (i) include sodium salt, potassium salt and ammonium salt of dioctylsulfosuccinic acid, diamylsulfosuccinic acid, and dicyclopentylsulfosuccinic acid.

  In the binder composition of the present invention, the content of the sulfosuccinic acid ester or a salt thereof is 0.01 to 10 parts by weight with respect to 100 parts by weight of the total of the particulate polymer and the water-soluble polymer. The content of the sulfosuccinic acid ester or a salt thereof is preferably 0.02 parts by weight or more, more preferably 0.05 parts by weight or more, with respect to 100 parts by weight in total of the particulate polymer and the water-soluble polymer. And it is preferably 5 parts by weight or less, more preferably 1 part by weight or less. By setting the content ratio of the sulfosuccinic acid ester or salt thereof to the lower limit or more, the adhesion of the electrode to the current collector can be improved. On the other hand, by setting the content ratio of the sulfosuccinic acid ester or a salt thereof to the upper limit or less, precipitation of lithium ions in the electrolytic solution can be reduced.

[1.4. water〕
The binder composition of the present invention contains water. Water functions as a solvent or a dispersion medium, and can disperse the particulate polymer or dissolve the water-soluble polymer.

  As the solvent, a solvent other than water may be used in combination with water. For example, when a liquid that can dissolve a particulate polymer and a water-soluble polymer is combined with water, the particulate polymer and the water-soluble polymer are adsorbed on the surface of the electrode active material, thereby stabilizing the dispersion of the electrode active material. Therefore, it is preferable.

  The type of liquid to be combined with water is preferably selected from the viewpoint of drying speed and environment. Preferred examples include cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethyl methyl ketone and cyclohexanone; ethyl acetate, butyl acetate, γ-butyrolactone, Esters such as ε-caprolactone; Nitriles such as acetonitrile and propionitrile; Ethers such as tetrahydrofuran and ethylene glycol diethyl ether: Alcohols such as methanol, ethanol, isopropanol, ethylene glycol, and ethylene glycol monomethyl ether; N-methyl Examples include amides such as pyrrolidone and N, N-dimethylformamide; among them, N-methylpyrrolidone (NMP) is preferable. One of these may be used alone, or two or more of these may be used in combination at any ratio.

  The amount of the solvent can be appropriately adjusted so that the concentration and viscosity are suitable for the production of the binder composition and the slurry composition using the binder composition. Specifically, the concentration of the solid content (that is, the substance remaining as a constituent component of the electrode active material layer after drying of the slurry composition) in the total amount of the binder composition of the present invention is preferably 40% by weight or more, More preferably, it is 45% by weight or more, preferably 75% by weight or less, more preferably 70% by weight or less.

[1.5. Method for producing binder composition]
The binder composition of the present invention can be produced by any production method. For example, it can be produced by mixing the above-described components in any order.
A particularly preferable production method includes a production method including the following step (1) and step (2).
Step (1): A step of mixing the particulate polymer, sulfosuccinic acid ester or salt thereof, and water to obtain a mixture (1).
Step (2): The mixture (1) and the water-soluble polymer are mixed, and the content ratio of the sulfosuccinic acid ester or a salt thereof is 0.01 to 100 parts by weight with respect to a total of 100 parts by weight of the particulate polymer and the water-soluble polymer. Obtaining a mixture (2) which is 10 parts by weight.
By mixing in this order, homogeneous mixing can be easily achieved.

  In the step (1), when the particulate polymer is used in the state of an aqueous dispersion, the step can be performed by mixing the aqueous dispersion with a sulfosuccinic acid ester or a salt thereof. Water may be added separately. Moreover, you may further add other components, such as water, in a process (2) or after a process (2) as needed.

  Examples of equipment for mixing include mixing equipment such as a ball mill, a sand mill, a bead mill, a roll mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, and a planetary mixer.

[2. Slurry composition for lithium ion secondary battery electrode]
The slurry composition of the present invention is a slurry composition for a lithium ion secondary battery electrode, and includes the binder composition of the present invention and an electrode active material.

[2.1. Positive electrode active material)
Of the electrode active materials, as the positive electrode active material (hereinafter sometimes simply referred to as “positive electrode active material”), a material capable of inserting and desorbing lithium ions is usually used. Such positive electrode active materials are roughly classified into those made of inorganic compounds and those made of organic compounds.

  Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, transition metal sulfides, lithium-containing composite metal oxides of lithium and transition metals, and the like. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.

Examples of the transition metal oxide include MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O _{13 and the} like can be mentioned. Among them, MnO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ are preferable from the viewpoint of cycle stability and capacity.

Examples of the transition metal sulfide include TiS ₂ , TiS ₃ , amorphous MoS ₂ , FeS, and the like.

  Examples of the lithium-containing composite metal oxide include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure.

Examples of the lithium-containing composite metal oxide having a layered structure include lithium-containing cobalt oxide (LCO: LiCoO ₂ ), lithium-containing nickel oxide (LiNiO ₂ ), and Co—Ni—Mn lithium composite oxide (NMC: LiNi _0.8 Co _0.1 Mn _0.1 O _2, LiNi _0.33 Co _0.33 Mn _0.33 O _2, etc.), Ni—Mn—Al lithium composite oxide, Ni—Co—Al lithium A composite oxide (NCA: Li [Ni—Co—Al] O ₂ or the like) can be used.

Examples of the lithium-containing composite metal oxide having a spinel structure include lithium manganate (LMO: LiMn ₂ O ₄ ) or Li [Mn _{3 / 2} M _1/2 ] O ₄ (where M is Cr, Fe, Co, Ni, Cu, etc.).

Examples of the lithium-containing composite metal oxide having an olivine type structure include Li _X MPO ₄ (wherein M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti). Represents at least one selected from the group consisting of Al, Si, B and Mo, and X represents a number satisfying 0 ≦ X ≦ 2, for example, LFP: LiFePO ₄ etc.) Is mentioned.

  Examples of the positive electrode active material made of an organic compound include conductive polymer compounds such as polyacetylene and poly-p-phenylene.

Moreover, you may use the positive electrode active material which consists of a composite material which combined the inorganic compound and the organic compound.
Alternatively, for example, a composite material covered with a carbon material may be produced by reducing and firing an iron-based oxide in the presence of a carbon source material, and the composite material may be used as a positive electrode active material. Iron-based oxides tend to have poor electrical conductivity, but can be used as a high-performance positive electrode active material by using a composite material as described above.

Furthermore, you may use as a positive electrode active material what carried out the element substitution of the said compound partially.
Moreover, you may use the mixture of said inorganic compound and organic compound as a positive electrode active material.
As the positive electrode active material, one type may be used alone, or two or more types may be used in combination at any ratio.

  Particularly preferred examples of the positive electrode active material include LCO, LMO, NMC, NCA, and LFP.

  The volume average particle diameter of the positive electrode active material particles is preferably 1 μm or more, more preferably 2 μm or more, and preferably 50 μm or less, more preferably 30 μm or less. By setting the average particle diameter of the positive electrode active material particles in the above range, the amount of the binder in preparing the positive electrode active material layer can be reduced, and the decrease in the capacity of the lithium ion secondary battery can be suppressed. Further, by making the average particle diameter of the positive electrode active material particles in the above range, it becomes easy to adjust the viscosity of the slurry composition of the present invention to an appropriate viscosity that is easy to apply, and a uniform positive electrode can be obtained. it can. Here, the volume average particle diameter employs a particle diameter at which the cumulative volume calculated from the small diameter side is 50% in the particle size distribution measured by the laser diffraction method.

  The amount of the positive electrode active material is a ratio of the positive electrode active material in the electrode active material layer, and is preferably 90% by weight or more, more preferably 95% by weight or more, and preferably 99.9% by weight or less, more preferably 99%. % By weight or less. By setting the amount of the positive electrode active material in the above range, the capacity of the lithium ion secondary battery can be increased, and the flexibility of the positive electrode and the adhesion between the current collector and the positive electrode active material layer can be improved.

[2.2. Negative electrode active material)
Among the electrode active materials, an electrode active material for a negative electrode (hereinafter also referred to as “negative electrode active material” as appropriate) is a substance that transfers electrons in the negative electrode. As the negative electrode active material, a material that can occlude and release lithium ions is usually used.
An example of a suitable negative electrode active material is carbon. Examples of carbon include natural graphite, artificial graphite, and carbon black. Among these, natural graphite is preferably used.

  Further, as the negative electrode active material, it is preferable to use a negative electrode active material containing at least one selected from the group consisting of tin, silicon, germanium, and lead. This is because a negative electrode active material containing these elements has a small irreversible capacity. Among these, a negative electrode active material containing silicon is preferable. By using a negative electrode active material containing silicon, the electric capacity of the lithium ion secondary battery can be increased.

  A negative electrode active material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Therefore, two or more kinds of the negative electrode active materials may be used in combination. Among these, it is preferable to use a negative electrode active material containing a combination of carbon and one or both of metallic silicon and a silicon-based active material. In a negative electrode active material containing a combination of carbon and one or both of metallic silicon and a silicon-based active material, Li insertion and desorption from one or both of metallic silicon and a silicon-based active material occurs at a high potential, It is presumed that Li insertion and desorption from carbon occur at low potential. For this reason, since expansion and contraction are suppressed, the cycle characteristics of the lithium ion secondary battery can be improved.

Examples of the silicon-based active material include SiO, SiO ₂ , SiO _x (0.01 ≦ x <2), SiC, SiOC, and the like, and SiO _x , SiC, and SiOC are preferable. Among these, it is particularly preferable to use SiO _x as the silicon-based active material from the viewpoint of suppressing the swelling of the negative electrode active material itself. SiO _x is a compound formed using one or both of SiO and SiO ₂ and metallic silicon as raw materials. This SiO _x can be produced, for example, by cooling and precipitating silicon monoxide gas generated by heating a mixture of SiO ₂ and metal silicon.

When carbon is used in combination with one or both of metallic silicon and a silicon-based active material, it is preferable that one or both of metallic silicon and the silicon-based active material is combined with conductive carbon. By combining with conductive carbon, swelling of the negative electrode active material itself can be suppressed.
Examples of the compounding method include a method of compounding one or both of metallic silicon and silicon-based active material with carbon; conductive carbon and one or both of metallic silicon and silicon-based active material The method of compounding by granulating a mixture; etc. are mentioned.

  Examples of the method for coating one or both of metallic silicon and silicon-based active material with carbon include, for example, a method in which one or both of metallic silicon and silicon-based active material are subjected to heat treatment, and disproportionation; A method of performing chemical vapor deposition by subjecting one or both of the materials to a heat treatment; and the like.

As specific examples of these methods, SiO _x is preferably at least 900 ° C., more preferably at least 1000 ° C., and even more preferably at least 1050 ° C. in an atmosphere containing at least one or both of organic gas and organic vapor. Particularly preferred is a method in which heat treatment is performed at a temperature of 1100 ° C. or higher, preferably 1400 ° C. or lower, more preferably 1300 ° C. or lower, and even more preferably 1200 ° C. or lower. According to this method, SiO _x can be disproportionated into a composite of silicon and silicon dioxide, and carbon can be chemically deposited on the surface.

  Another specific example is the following method. That is, one or both of metallic silicon and silicon-based active material is heat-treated in an inert gas atmosphere to disproportionate to obtain a silicon composite (the temperature range of heat treatment in this step is preferably 900). ℃ or higher, more preferably 1000 ℃ or higher, even more preferably 1100 ℃ or higher, and preferably 1400 ℃ or lower, more preferably 1300 ℃ or lower. The silicon composite thus obtained is preferably pulverized to a particle size of 0.1 μm to 50 μm. The pulverized silicon composite is heated at 800 ° C. to 1400 ° C. under an inert gas stream. The heated silicon composite is subjected to a heat treatment in an atmosphere containing at least one or both of an organic gas and an organic vapor to chemically deposit carbon on the surface (the temperature range of the heat treatment in this step is preferably 800). Or higher, more preferably 900 ° C. or higher, even more preferably 1000 ° C. or higher, and preferably 1400 ° C. or lower, more preferably 1300 ° C. or lower, and preferably 1200 ° C. or lower.

  Moreover, the following method is also mentioned as another specific example. That is, one or both of metal silicon and silicon-based active material is subjected to chemical vapor deposition treatment with one or both of organic gas and organic vapor (the temperature range of the treatment is preferably 500 ° C. to 1200 ° C., more preferably 500 ° C. C. to 1000.degree. C., even more preferably 500.degree. C. to 900.degree. This is subjected to heat treatment in an inert gas atmosphere to disproportionate (the heat treatment temperature range in this step is preferably 900 ° C. or higher, more preferably 1000 ° C. or higher, and even more preferably 1100 ° C. or higher. And preferably 1400 ° C. or lower, more preferably 1300 ° C. or lower).

  In the case of using a negative electrode active material containing a combination of carbon and one or both of metallic silicon and a silicon-based active material, the amount of silicon atoms in the negative electrode active material is 0.1 parts by weight with respect to 100 parts by weight of the total carbon atoms. It is preferable that it is -50 weight part. Thereby, a conductive path is formed satisfactorily and the conductivity of the negative electrode can be improved.

  When a negative electrode active material including a combination of carbon and one or both of metallic silicon and a silicon-based active material is used, a weight ratio of carbon to one or both of metallic silicon and a silicon-based active material (“carbon weight” / “Weight of metal silicon and silicon-based active material”) is preferably 50/50 or more, more preferably 70/30 or more, and preferably 97/3 or less, more preferably 90/10 or less. Thereby, the cycling characteristics of a lithium ion secondary battery can be improved.

The negative electrode active material is preferably sized in the form of particles. When the shape of the particles is spherical, a higher-density electrode can be formed at the time of forming the electrode for a lithium ion secondary battery.
The volume average particle diameter of the particles of the negative electrode active material is appropriately selected in consideration of other constituent requirements of the lithium ion secondary battery, and is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 5 μm or more. And preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 20 μm or less.

The specific surface area of the negative electrode active material, the output from the viewpoint of improving the density, preferably ^2m 2 / g or more, more preferably ^3m 2 / g or more, still more preferably ^{5 m} 2 / g or more, and preferably ^{20 m} 2 / g or less, more preferably 15 m ² / g or less, and even more preferably 10 m ² / g or less. The specific surface area of the negative electrode active material can be measured by, for example, the BET method.

  The amount of the negative electrode active material is a ratio of the negative electrode active material in the electrode active material layer, and is preferably 85% by weight or more, more preferably 88% by weight or more, and preferably 99% by weight or less, more preferably 97% by weight. It is as follows. By setting the amount of the negative electrode active material in the above range, it is possible to realize a negative electrode that exhibits flexibility and adhesion while exhibiting a high capacity.

[2.3. Ratio of binder composition in slurry composition]
The ratio of the binder composition contained in the slurry composition of the present invention can be adjusted as appropriate so that the performance of the obtained battery is satisfactorily exhibited. For example, it can be set as 0.5-10 weight part as a ratio of binder composition solid content with respect to 100 weight part of electrode active materials.

[2.4. (Optional ingredients)
The slurry composition of this invention can contain arbitrary components other than the electrode active material mentioned above and a binder composition.
For example, the slurry composition of the present invention may contain a thickening agent other than that added as the water-soluble polymer. By including a thickener, the viscosity of the slurry composition can be adjusted to a range suitable for coating. Examples of the thickener include known thickeners such as carboxymethylcellulose. The amount of the thickener (corresponding to the solid content) is suitably adjusted so as to obtain an appropriate viscosity, preferably in the range of 0.1 to 5 parts by weight, with respect to 100 parts by weight of the electrode active material. .

  The slurry composition of the present invention may further contain a solvent such as water in addition to the water contained in the binder composition of the present invention. The amount of the solvent is preferably adjusted so that the viscosity of the slurry composition of the present invention becomes a viscosity suitable for coating. Specifically, the concentration of the solid content of the slurry composition of the present invention (that is, the substance remaining as a constituent component of the electrode active material layer after drying of the slurry composition) is preferably 30% by weight or more, more preferably The amount is adjusted to 35% by weight or more, preferably 70% by weight or less, more preferably 65% by weight or less.

Further, for example, the slurry composition of the present invention can contain a conductive material. The conductive material is a component that can improve electrical contact between the electrode active materials. By including a conductive material, the discharge rate characteristics of the lithium ion secondary battery can be improved.
Examples of the conductive material include furnace black, acetylene black, ketjen black, oil furnace black, carbon black, graphite, vapor grown carbon fiber, and conductive carbon such as carbon nanotube. Among them, acetylene black, oil furnace black, and ketjen black are preferable, and acetylene black and ketjen black are particularly preferable because the balance between the low-temperature output characteristics and the life characteristics of the lithium ion secondary battery is good. Moreover, a conductive material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The specific surface area of the conductive material is preferably ^{50 m} 2 / g or more, more preferably ^{60 m} 2 / g or more, particularly preferably at ^70m 2 / g or more, and preferably 1500 m ² / g or less, more preferably 1200 m ² / g or less, particularly preferably 1000 m ² / g or less. By setting the specific surface area of the conductive material to be equal to or higher than the lower limit of the above range, the low temperature output characteristics of the lithium ion secondary battery can be improved. Moreover, the binding property of a collector and a negative electrode active material layer can be improved by setting it as an upper limit or less.

  The amount of the conductive material is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, even more preferably 0.3 parts by weight or more, and preferably 100 parts by weight or less of the negative electrode active material. Is 10 parts by weight or less, more preferably 8 parts by weight or less, and even more preferably 5 parts by weight or less. By setting the amount of the conductive material to the lower limit value or more, the low temperature output characteristics of the lithium ion secondary battery can be improved. Moreover, the binding property of a collector and a negative electrode active material layer can be improved by making the quantity of a electrically conductive material below the said upper limit.

[2.5. Method for producing slurry composition]
The slurry composition of the present invention can be produced, for example, by mixing an electrode active material, a binder composition, and optional components (water, thickener and other optional components) as necessary. The specific procedure at this time is arbitrary. For example, when manufacturing a slurry composition containing an electrode active material, a binder composition, water, a thickener and a conductive material, the electrode active material, the binder composition, the thickener and the conductive material are added to water at the same time. A method of mixing; a method in which an electrode active material, a conductive material, and a thickener are added to water and mixed, and then a binder composition is added and mixed;

  Examples of equipment for mixing include mixing equipment such as a ball mill, a sand mill, a bead mill, a roll mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, and a planetary mixer.

[3. Electrode for lithium ion secondary battery]
The electrode for a lithium ion secondary battery of the present invention is obtained by applying a slurry composition for a lithium ion secondary battery on a current collector and drying it.

[3.1. Current collector]
The current collector is not particularly limited as long as it has electrical conductivity and is electrochemically durable, but a metal material is preferable because it has heat resistance. Examples of the material for the current collector include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum. Among them, the current collector used for the positive electrode is preferably aluminum, and the current collector used for the negative electrode is preferably copper. One kind of the above materials may be used alone, or two or more kinds thereof may be used in combination at any ratio.

The shape of the current collector is not particularly limited, but a sheet shape having a thickness of about 0.001 mm to 0.5 mm is preferable.
In order to increase the adhesion strength with the electrode active material layer, the current collector is preferably used after roughening the surface in advance. Examples of the roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. In the mechanical polishing method, for example, an abrasive cloth paper to which abrasive particles are fixed, a grindstone, an emery buff, a wire brush provided with a steel wire, or the like is used. In order to increase the adhesion strength and conductivity of the electrode active material layer, an intermediate layer may be formed on the surface of the current collector.

[3.2. Application of slurry composition)
After preparing the current collector, a film of the slurry composition of the present invention is formed on the current collector. Under the present circumstances, the film | membrane of a slurry composition is normally formed by apply | coating the slurry composition of this invention. Moreover, a slurry composition may be apply | coated to the single side | surface of a collector, and may be apply | coated to both surfaces.

There is no restriction | limiting in the coating method, For example, methods, such as a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, are mentioned.
Further, the thickness of the slurry composition film can be appropriately set according to the thickness of the target electrode active material layer.

[3.3. (Drying the membrane)
After forming the slurry composition film, the liquid such as water is removed from the film by drying. Thereby, the electrode active material layer containing the solid content of an electrode active material and a binder composition is formed in the surface of an electrical power collector, and an electrode is obtained.

Examples of the drying method include drying with warm air, hot air, low-humidity air or the like; vacuum drying; (far) drying method by irradiation with infrared rays or electron beams. Among these, a drying method by irradiation with far infrared rays is preferable.
The drying temperature and drying time are preferably a temperature and a time at which water can be removed from the slurry composition film. Specifically, the drying time is preferably 1 minute to 30 minutes, and the drying temperature is preferably 40 ° C to 180 ° C.

[3.4. Arbitrary process]
After drying the slurry composition film, it is preferable to apply pressure treatment to the electrode active material layer, for example, using a die press or a roll press, if necessary. By the pressure treatment, the porosity of the electrode active material layer can be lowered. The porosity is preferably 5% or more, more preferably 7% or more, and preferably 30% or less, more preferably 20% or less. By setting the porosity to be equal to or higher than the lower limit of the above range, a high volume capacity can be easily obtained, and the electrode active material layer can be made difficult to peel from the current collector. Moreover, high charging efficiency and discharge efficiency are acquired by setting it as an upper limit or less.

  Furthermore, when the electrode active material layer includes a polymer that can be cured by a curing reaction such as a crosslinking reaction, the polymer may be cured after the electrode active material layer is formed.

[3.5. Other matters related to electrodes]
The thickness of the electrode active material layer formed as described above can be arbitrarily set according to the required battery performance.
For example, the thickness of the positive electrode active material layer is preferably 5 μm or more, more preferably 10 μm or more, and preferably usually 300 μm or less, more preferably 250 μm or less. When the thickness of the positive electrode active material layer is in the above range, high characteristics can be realized in both load characteristics and energy density.
Further, for example, the thickness of the negative electrode active material layer is preferably 5 μm or more, more preferably 20 μm or more, particularly preferably 30 μm or more, and preferably 1000 μm or less, more preferably 500 μm or less, still more preferably 300 μm or less, particularly Preferably it is 250 micrometers or less. When the thickness of the negative electrode active material layer is in the above range, load characteristics and cycle characteristics can be improved.

  The amount of water in the electrode active material layer is preferably 1000 ppm or less, and more preferably 500 ppm or less. By setting the moisture content of the electrode active material layer within the above range, an electrode having excellent durability can be realized. The amount of water can be measured by a known method such as the Karl Fischer method. Such a low water content can be achieved by appropriately adjusting the composition of the structural unit in the water-soluble polymer. In particular, the fluorine-containing (meth) acrylic acid ester monomer unit is preferably 0.5% by weight or more, more preferably 1% by weight or more, and preferably 20% by weight or less, more preferably 10% by weight or less. By setting it within a certain range, the water content can be reduced.

[4. Lithium ion secondary battery]
The lithium ion secondary battery of this invention is equipped with a positive electrode, a negative electrode, and electrolyte solution. Moreover, the lithium ion secondary battery of this invention can be equipped with a separator. However, one or both of the negative electrode and the positive electrode is an electrode for a lithium ion secondary battery of the present invention. By providing the electrode of the present invention, the lithium ion secondary battery of the present invention has a cycle characteristic and a low temperature output characteristic due to characteristics such as the low temperature acceptance characteristic of the electrode and the affinity between the electrode active material layer and the electrolyte. The battery can be excellent in

[4.1. Electrolyte)
As the electrolytic solution, for example, a solution obtained by dissolving a lithium salt as a supporting electrolyte in a non-aqueous solvent may be used. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and other lithium salts. In particular, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferably used. One of these may be used alone, or two or more of these may be used in combination at any ratio.

  The amount of the supporting electrolyte is preferably 1% by weight or more, more preferably 5% by weight or more, and preferably 30% by weight or less, more preferably 20% by weight or less with respect to the electrolytic solution. If the amount of the supporting electrolyte is too small or too large, the ionic conductivity is lowered, and the charging characteristics and discharging characteristics of the secondary battery may be lowered.

  The solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. Examples of the solvent include alkyl carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (MEC); Examples include esters such as butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; and the like. In particular, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferred because high ion conductivity is easily obtained and the use temperature range is wide. A solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  Moreover, you may make an electrolyte solution contain an additive as needed. As the additive, for example, carbonate compounds such as vinylene carbonate (VC) are preferable. An additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Examples of the electrolytic solution other than the above include a gel polymer electrolyte obtained by impregnating a polymer electrolyte such as polyethylene oxide and polyacrylonitrile with an electrolytic solution; an inorganic solid electrolyte such as lithium sulfide, LiI, and Li ₃ N; Can do.

[4.2. separator〕
As the separator, a porous substrate having a pore portion is usually used. Examples of separators include (a) a porous separator having pores, (b) a porous separator having a polymer coating layer formed on one or both sides, and (c) a porous resin coat containing inorganic ceramic powder. And a porous separator having a layer formed thereon. Examples of these include solid polymer electrolytes such as polypropylene, polyethylene, polyolefin, or aramid porous separators, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride hexafluoropropylene copolymers. Or a polymer film for a gel polymer electrolyte; a separator coated with a gelled polymer coat layer; a separator coated with a porous film layer composed of an inorganic filler and an inorganic filler dispersant; and the like.

[4.3. Method for producing lithium ion secondary battery]
The manufacturing method of the lithium ion secondary battery of the present invention is not particularly limited. For example, the above-described negative electrode and positive electrode may be overlapped via a separator, and this may be wound or folded in accordance with the shape of the battery and placed in the battery container, and the electrolyte may be injected into the battery container and sealed. Furthermore, if necessary, an expanded metal; an overcurrent prevention element such as a fuse or a PTC element; a lead plate or the like may be inserted to prevent an increase in pressure inside the battery or overcharge / discharge. The shape of the battery may be any of, for example, a laminate cell type, a coin type, a button type, a sheet type, a cylindrical type, a square type, and a flat type.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.
In the following description, “%” and “part” representing amounts are based on weight unless otherwise specified. In addition, the operations described below were performed under normal temperature and normal pressure conditions unless otherwise specified.

[Evaluation method]
(1) Low temperature acceptance characteristics (negative electrode)
The lithium ion secondary batteries of the laminate type cells produced in the examples and comparative examples were allowed to stand for 24 hours in an environment at 25 ° C., and then 4.35 V, 1 C, and 1 hour in an environment at −10 ° C. The charging operation was performed. Thereafter, the negative electrode was taken out in an argon atmosphere at room temperature, the area S (cm ² ) where lithium metal was deposited was measured, and evaluated according to the following evaluation criteria. The smaller the deposited area, the better the low-temperature acceptance characteristics.

(Evaluation criteria)
A: 0 ≦ S <1 (cm ² )
B: 1 ≦ S <5 (cm ² )
C: 5 ≦ S <10 (cm ² )
D: 10 ≦ S <15 (cm ² )
E: 15 ≦ S <20 (cm ² )
F: 20 ≦ S ≦ 25 (cm ² )

(2) Low temperature acceptance characteristics (positive electrode)
Evaluation was performed in the same manner as the low-temperature acceptance characteristics of the negative electrode. However, the evaluation criteria were changed as follows.

(Evaluation criteria)
A: 0 ≦ S <1 (cm ² )
B: 1 ≦ S <3 (cm ² )
C: 3 ≦ S <6 (cm ² )
D: 6 ≦ S <9 (cm ² )
E: 9 ≦ S <12 (cm ² )
F: 12 ≦ S ≦ 21.16 (cm ² )

(3) Contact angle of binder composition film with electrolyte solution The binder compositions produced in the examples and comparative examples were dried at room temperature for 7 days to prepare binder composition films. By using a contact angle meter (“DM-701” manufactured by Kyowa Interface Chemical Co., Ltd.), EC / DEC / VC = 68.5 / 30 / 1.5 volume ratio (electrolytic solvent) is formed on the binder composition film. 25 μC) was dropped, and the contact angle W (°) after 10 seconds was measured. The smaller this value, the greater the wettability between the binder composition and the electrolytic solution, and the better the low temperature characteristics.

(4) Low-temperature output characteristics After the lithium ion secondary batteries of the laminate type cells produced in Examples and Comparative Examples were allowed to stand for 24 hours in an environment at 25 ° C, 0.1C The battery was charged at a constant current for 5 hours, and the voltage V0 when charging was completed was measured. Thereafter, a discharge operation was performed at a discharge rate of 1 C in a -10 ° C environment, and the voltage V1 15 seconds after the start of discharge was measured. The low temperature output characteristics were evaluated by a voltage change (mV) indicated by ΔV = V0−V1. It shows that it is excellent in low temperature output characteristics, so that this value is small.

(5) Cycle characteristics After the lithium ion secondary batteries of the laminate type cells produced in the examples and comparative examples were allowed to stand for 24 hours in an environment of 25 ° C, the constant current of 1C was obtained in the environment of 25 ° C. The battery was charged until the voltage reached 4.35V, and was charged / discharged at a constant current of 1C until the voltage reached 2.75V. The initial capacity C0 was measured. Further, charging and discharging under the above conditions were repeated in a 45 ° C. environment, and the capacity C2 after 500 cycles was measured. The high-temperature cycle characteristics were evaluated by a capacity retention rate represented by ΔC = C2 / C0 × 100 (%). It shows that it is excellent in cycling characteristics, and by extension, life characteristics, so that this value is high.

(6) Viscosity of water-soluble polymer The viscosity was measured with a B-type viscometer at 25 ° C and 60 rpm.

(7) Low temperature acceptance characteristics (separator)
The lithium ion secondary batteries of the laminate type cells produced in the examples and comparative examples were allowed to stand for 24 hours in an environment at 25 ° C., and then 4.35 V, 1 C, and 1 hour in an environment at −10 ° C. The charging operation was performed. Thereafter, the separator was taken out under a room temperature argon environment, and the area S (cm ² ) on which the lithium metal was deposited was measured and evaluated according to the following evaluation criteria. The smaller the deposited area, the better the low-temperature acceptance characteristics.

(Evaluation criteria)
A: 0 ≦ S <1 (cm ² )
B: 1 ≦ S <5 (cm ² )
C: 5 ≦ S <10 (cm ² )
D: 10 ≦ S <15 (cm ² )
E: 15 ≦ S <20 (cm ² )
F: 20 ≦ S ≦ 25 (cm ² )

<Example 1>
(1-1. Production of water-soluble polymer)
In a 5 MPa pressure vessel with a stirrer, 32.5 parts of methacrylic acid (acidic functional group-containing monomer), 7.5 parts of 2,2,2-trifluoroethyl methacrylate (fluorine-containing (meth) acrylic acid ester monomer) , Ethyl acrylate (other monomers) 58.2 parts, ethylene dimethacrylate (crosslinkable monomer) 0.8 parts, polyoxyalkylene alkenyl ether ammonium sulfate as a reactive surfactant (Latemul PD manufactured by Kao Corporation) -104 ") 1.0 part, 0.6 part of t-dodecyl mercaptan, 150 parts of ion-exchanged water, and 1.0 part of potassium persulfate (polymerization initiator), and after stirring sufficiently, the mixture was heated to 60 ° C. The polymerization was started by warming. When the polymerization conversion reached 96%, the reaction was stopped by cooling to obtain a mixture containing a water-soluble polymer. 10% aqueous ammonia was added to the mixture containing the water-soluble polymer to adjust the pH to 8 to obtain an aqueous solution containing the desired water-soluble polymer.
A part of the obtained aqueous solution containing the water-soluble polymer was taken, water was added to make a 1% aqueous solution, and this was used as a sample to measure the viscosity. As a result, it was 68 mPa · s.

(1-2. Production of particulate polymer)
In a 5 MPa pressure vessel with a stirrer, 33.0 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 62.5 parts of styrene, 1 part of 2-hydroxyethyl acrylate, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, After adding 150 parts of ion exchange water and 0.5 part of potassium persulfate as a polymerization initiator and stirring sufficiently, the mixture was heated to 50 ° C. to initiate polymerization. When the polymerization conversion reached 96%, the reaction was stopped by cooling to obtain a mixture containing a particulate polymer (SBR). After adding 5% aqueous sodium hydroxide solution to the mixture containing the particulate polymer and adjusting the pH to 8, the unreacted monomer is removed by heating under reduced pressure, and then cooled to 30 ° C. or lower to obtain a desired value. An aqueous dispersion containing the particulate polymer was obtained. The obtained particulate polymer had a volume average particle diameter D50 of 145 nm.

(1-3. Production of binder composition for secondary battery)
In a container, add the aqueous dispersion of the particulate polymer prepared in the above (1-2) in an amount corresponding to a solid content of 95 parts, and 0.25 part of sodium dioctylsulfosuccinate, and then mix. The aqueous solution of the water-soluble polymer prepared in (1-1) above is added in an amount corresponding to 5 parts by solid content, and water is mixed to obtain a secondary battery binder composition having a solid content concentration of 25%. It was.
About this binder composition, the contact angle was measured by the method mentioned above.

(1-4. Production of slurry composition for negative electrode)
In a planetary mixer with a disper, 100 parts of natural graphite (volume average particle diameter: 15.6 μm) having a specific surface area of 5.5 m ² / g as a negative electrode active material, and carboxymethyl cellulose (“MAC” manufactured by Nippon Paper Chemical Co., Ltd.) as a thickener -350HC ") was added in an amount of 1.0 part in terms of solid content, and ion exchange water was added to obtain a solid content concentration of 60%, followed by mixing at 25 ° C for 60 minutes. Next, ion-exchanged water was added to adjust the solid content concentration to 52%, and the mixture was further mixed at 25 ° C. for 15 minutes to obtain a mixed solution. To the mixed solution, 2.0 parts by weight (solid content equivalent amount) of the above-mentioned (1-3) binder composition for secondary battery and ion-exchanged water are added to obtain a final solid content concentration of 48%, and further mixed for 10 minutes. did. This was defoamed under reduced pressure to obtain a slurry composition for negative electrode having good fluidity.

(1-5. Production of negative electrode)
The slurry composition for negative electrode obtained in the above (1-4) is applied on a copper foil having a thickness of 20 μm, which is a current collector, with a comma coater so that the film thickness after drying becomes about 150 μm. , Dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a negative electrode before pressing. The negative electrode raw material before pressing was rolled with a roll press to obtain a negative electrode after pressing with a negative electrode active material layer having a thickness of 80 μm.

(1-6. Production of positive electrode slurry composition)
100 parts of LiCoO ₂ having a volume average particle diameter of 12 μm as the positive electrode active material, ₂ parts of acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) as the conductive material, and polyvinylidene fluoride (manufactured by Kureha Co., # 7208) as the binder Was mixed with 2 parts corresponding to the solid content and N-methylpyrrolidone to adjust the total solid content concentration to 70%. These were mixed by a planetary mixer to prepare a positive electrode slurry composition.

(1-7. Production of positive electrode)
The positive electrode slurry composition obtained in (1-6) above was applied onto a 20 μm thick aluminum foil as a current collector with a comma coater so that the film thickness after drying was about 150 μm. , Dried. This drying was performed by transporting the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Then, it heat-processed for 2 minutes at 120 degreeC, and obtained the positive electrode.

(1-8. Preparation of separator)
A single-layer polypropylene separator (“Celguard 2500” manufactured by Celgard) was cut into a 5 × 5 cm ² square.

(1-9. Lithium ion secondary battery)
An aluminum packaging exterior was prepared as the battery exterior. The positive electrode obtained in the above (1-7) was cut into a 4.6 × 4.6 cm ² square to obtain a square positive electrode. This square positive electrode was placed so that the current collector-side surface was in contact with the aluminum packaging exterior. The square separator obtained in (1-8) above was placed on the surface of the positive electrode active material layer side of the square positive electrode.
The negative electrode after pressing obtained in (1-5) above was cut into a 5 × 5 cm ² square to obtain a square negative electrode. This square negative electrode was placed on a square separator so that the surface on the negative electrode active material layer side faces the separator. An electrolyte solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 volume ratio (25 ° C.), electrolyte: LiPF _{6 at a} concentration of 1 M) was injected so that no air remained, and further, 150 ° C. The aluminum exterior was closed by heat sealing, and the opening of the aluminum packaging was sealed. Thereby, the lithium ion secondary battery was manufactured. About the obtained lithium ion secondary battery, the low temperature acceptance characteristic, the low temperature output characteristic, and the cycle characteristic were evaluated by the method described above. However, the low temperature acceptance characteristics were evaluated for the negative electrode.

<Example 2>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
-In the manufacture of the binder composition for secondary batteries of (1-3), the ratio of sodium dioctyl sulfosuccinate was changed to 0.015 part.

<Example 3>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
-In the manufacture of the binder composition for secondary batteries of (1-3), the ratio of sodium dioctyl sulfosuccinate was changed to 9 parts.

<Example 4>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the secondary battery binder composition of (1-3), sodium dicyclohexylsulfosuccinate was used instead of sodium dioctylsulfosuccinate.

<Example 5>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
-In manufacture of the binder composition for secondary batteries of (1-3), it replaced with sodium dioctyl sulfosuccinate and used the sodium diamyl sulfosuccinate.

<Example 6>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the secondary battery binder composition of (1-3), lithium dioctyl sulfosuccinate was used instead of sodium dioctyl sulfosuccinate.

<Example 7>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the binder composition for a secondary battery of (1-3), potassium dioctyl sulfosuccinate was used instead of sodium dioctyl sulfosuccinate.

<Example 8>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the secondary battery binder composition of (1-3), the proportion of the particulate polymer was changed to 98 parts (corresponding to the solid content), and the proportion of the water-soluble polymer produced in (1-1) Was changed to 2 parts (corresponding to solid content).

<Example 9>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the secondary battery binder composition of (1-3), the proportion of the particulate polymer was changed to 85 parts (corresponding to the solid content), and the proportion of the water-soluble polymer produced in (1-1) Was changed to 15 parts (corresponding to solid content).

<Example 10>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the secondary battery binder composition of (1-3), the proportion of the particulate polymer was changed to 75 parts (corresponding to the solid content), and the proportion of the water-soluble polymer produced in (1-1) Was changed to 25 parts (corresponding to solid content).

<Example 11>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the secondary battery binder composition of (1-3), the proportion of the particulate polymer was changed to 60 parts (corresponding to the solid content), and the proportion of the water-soluble polymer produced in (1-1) Was changed to 40 parts (corresponding to solid content).

<Example 12>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the water-soluble polymer (1-1), the ratio of methacrylic acid was changed to 30.0 parts, and 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) was used. . That is, the materials used in the production of the water-soluble polymer were 30.0 parts of methacrylic acid (acidic functional group-containing monomer), 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2, 2, 2 -7.5 parts of trifluoroethyl methacrylate (fluorine-containing (meth) acrylic acid ester monomer), 58.2 parts of ethyl acrylate (other monomer), 0.8 ethylene dimethacrylate (crosslinkable monomer) Part, 1.0 part of polyoxyalkylene alkenyl ether ammonium sulfate ("Latemul PD-104" manufactured by Kao Corporation), 0.6 part of t-dodecyl mercaptan, 150 parts of ion-exchanged water, and potassium persulfate as a reactive surfactant (Polymerization initiator) 1.0 part.

<Example 13>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
-In the manufacture of the water-soluble polymer of (1-1), 30.0 parts of acrylic acid and 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid were used instead, without using methacrylic acid. That is, the materials used in the production of the water-soluble polymer were 30.0 parts of acrylic acid (acid functional group-containing monomer), 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2, 2, 2 -7.5 parts of trifluoroethyl methacrylate (fluorine-containing (meth) acrylic acid ester monomer), 58.2 parts of ethyl acrylate (other monomer), 0.8 ethylene dimethacrylate (crosslinkable monomer) Part, 1.0 part of polyoxyalkylene alkenyl ether ammonium sulfate ("Latemul PD-104" manufactured by Kao Corporation), 0.6 part of t-dodecyl mercaptan, 150 parts of ion-exchanged water, and potassium persulfate as a reactive surfactant (Polymerization initiator) 1.0 part.

<Example 14>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the water-soluble polymer (1-1), the proportion of methacrylic acid was changed to 22 parts, and the proportion of ethyl acrylate was changed to 68.7 parts.

<Example 15>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the water-soluble polymer (1-1), the proportion of methacrylic acid was changed to 68 parts, and the proportion of ethyl acrylate was changed to 22.7 parts.

<Example 16>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the water-soluble polymer (1-1), perfluorooctyl acrylate was used instead of 2,2,2-trifluoroethyl methacrylate.

<Example 17>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the water-soluble polymer (1-1), perfluoroethyl acrylate was used instead of 2,2,2-trifluoroethyl methacrylate.

<Example 18>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the water-soluble polymer (1-1), the proportion of 2,2,2-trifluoroethyl methacrylate was changed to 0.15 parts, and the proportion of ethyl acrylate was changed to 65.55 parts.

<Example 19>
A lithium ion secondary battery and its components were manufactured and evaluated in the same manner as Example 1 except for the following points.
In the production of the water-soluble polymer (1-1), the proportion of 2,2,2-trifluoroethyl methacrylate was changed to 28 parts, and the proportion of ethyl acrylate was changed to 37.7 parts.

<Example 20>
(20-1. Production of particulate polymer)
In a 5 MPa pressure vessel with a stirrer, 77 parts of 2-ethylhexyl acrylate, 20 parts of acrylonitrile, 2.0 parts of itaconic acid, and 1 part of 2-hydroxyethyl acrylate, 1 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, And 0.8 parts of potassium persulfate was added as a polymerization initiator, and it fully stirred. Then, it heated to 50 degreeC and superposition | polymerization was started. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing a particulate polymer. The mixture containing the particulate polymer was adjusted to pH 8 by adding a 5% aqueous sodium hydroxide solution. Then, after removing the unreacted monomer from the mixture containing the particulate polymer by heating under reduced pressure, the mixture was cooled to 30 ° C. or lower to obtain an aqueous dispersion containing the desired particulate polymer. . The obtained particulate polymer had a volume average particle diameter D50 of 200 nm and a glass transition temperature of −20 ° C.

(20-2. Production of binder composition for secondary battery)
In a container, add the aqueous dispersion of the particulate polymer prepared in (20-1) above in an amount of 95 parts in terms of solid content, and 0.25 parts of sodium dioctyl sulfosuccinate, and then mix. An aqueous solution of the water-soluble polymer prepared in (1-1) of Example 1 was added to an amount corresponding to 5 parts in terms of solid content, and water was added and mixed to form a binder composition for a secondary battery having a solid content concentration of 25%. I got a thing.
About this binder composition, the contact angle was measured by the method mentioned above.

(20-3. Production of slurry composition for negative electrode)
In a planetary mixer with a disper, 100 parts of natural graphite (volume average particle diameter: 15.6 μm) having a specific surface area of 5.5 m ² / g as a negative electrode active material, and carboxymethyl cellulose (“MAC” manufactured by Nippon Paper Chemical Co., Ltd.) as a thickener -350HC ") was added in an amount of 1.0 part in terms of solid content, and ion exchange water was added to obtain a solid content concentration of 60%, followed by mixing at 25 ° C for 60 minutes. Next, ion-exchanged water was added to adjust the solid content concentration to 52%, and further mixed at 25 ° C. for 15 minutes to obtain a mixed solution. An amount of the aqueous dispersion of the particulate polymer prepared in (1-2) of Example 1 to 2.0 parts in terms of solid content and ion-exchanged water are added to the above mixed liquid, and the final solid content concentration 48% and mixed for an additional 10 minutes. This was defoamed under reduced pressure to obtain a slurry composition for negative electrode having good fluidity.

(20-4. Production of negative electrode)
Apply the slurry composition for negative electrode obtained in (20-3) above on a copper foil with a thickness of 20 μm, which is a current collector, with a comma coater so that the film thickness after drying is about 150 μm. , Dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a negative electrode before pressing. The negative electrode raw material before pressing was rolled with a roll press to obtain a negative electrode after pressing with a negative electrode active material layer having a thickness of 80 μm.

(20-5. Production of slurry composition for positive electrode)
100 parts of LiCoO ₂ having a volume average particle diameter of 12 μm as the positive electrode active material, ₂ parts of acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) as the conductive material, and 2 obtained by (20-2) above as the binder The amount of the secondary battery binder composition corresponding to the solid content of 2 parts and N-methylpyrrolidone were mixed to adjust the total solid content concentration to 70%. These were mixed by a planetary mixer to prepare a positive electrode slurry composition.

(20-6. Production of positive electrode)
The positive electrode slurry composition obtained in (20-5) above was applied onto a 20 μm thick aluminum foil as a current collector with a comma coater so that the film thickness after drying was about 150 μm. , Dried. This drying was performed by transporting the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Then, it heat-processed for 2 minutes at 120 degreeC, and obtained the positive electrode.

(20-7. Preparation of separator)
A single-layer polypropylene separator (“Celguard 2500” manufactured by Celgard) was cut into a 5 × 5 cm ² square.

(20-8. Lithium ion secondary battery)
An aluminum packaging exterior was prepared as the battery exterior. The positive electrode obtained in (20-6) above was cut into a 4.6 × 4.6 cm ² square to obtain a square positive electrode. This square positive electrode was placed so that the current collector-side surface was in contact with the aluminum packaging exterior. On the surface of the square positive electrode on the positive electrode active material layer side, the square separator obtained in (20-7) above was placed.
The negative electrode after pressing obtained in (20-4) above was cut into a 5 × 5 cm ² square to obtain a square negative electrode. This square negative electrode was placed on a square separator so that the surface on the negative electrode active material layer side faces the separator. An electrolyte solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 volume ratio (25 ° C.), electrolyte: LiPF _{6 at a} concentration of 1 M) was injected so that no air remained, and further, 150 ° C. The aluminum exterior was closed by heat sealing, and the opening of the aluminum packaging was sealed. Thereby, the lithium ion secondary battery was manufactured. About the obtained lithium ion secondary battery, the low temperature acceptance characteristic, the low temperature output characteristic, and the cycle characteristic were evaluated by the method described above. However, the low temperature acceptance characteristics were evaluated for the positive electrode.

<Example 21>
A lithium ion secondary battery and its constituent elements were produced and evaluated in the same manner as in Example 20 except for the following points.
In the production of the positive electrode slurry composition of (20-5), LiFePO ₄ having a volume average particle diameter of 2 μm was used as the positive electrode active material instead of LiCoO ₂ having a volume average particle diameter of 12 μm.

<Example 22>
A lithium ion secondary battery and its constituent elements were produced and evaluated in the same manner as in Example 20 except for the following points.
In the production of the positive electrode slurry composition of (20-5), instead of LiCoO ₂ having a volume average particle size of 12 μm, LiNi _0.8 Co _0.1 Mn _{0. 1} O ₂ was used.

<Example 23>
A lithium ion secondary battery was manufactured and evaluated in the same manner as (1-9) of Example 1 except for the following points.
-As a positive electrode, it replaced with the positive electrode obtained by (1-7) of Example 1, and used what was obtained by (20-6) of Example 20. FIG.
-Low temperature acceptance characteristics were evaluated for each of the positive electrode and the negative electrode.

<Example 24>
(24-1. Production of particulate polymer)
In a 5 MPa pressure vessel with a stirrer, 92.8 parts butyl acrylate, 2 parts acrylonitrile, 2 parts methacrylic acid, 1.6 parts N-methylolacrylamide, 1.6 parts acrylamide, 1 part sodium dodecylbenzenesulfonate as an emulsifier, ion exchange 150 parts of water and 0.8 part of potassium persulfate as a polymerization initiator were added and sufficiently stirred. Then, it heated to 50 degreeC and superposition | polymerization was started. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing a particulate polymer. The mixture containing the particulate polymer was adjusted to pH 8 by adding a 5% aqueous sodium hydroxide solution. Then, after removing the unreacted monomer from the mixture containing the particulate polymer by heating under reduced pressure, the mixture was cooled to 30 ° C. or lower to obtain an aqueous dispersion containing the desired particulate polymer. . The obtained particulate polymer had a volume average particle diameter D50 of 350 nm and a glass transition temperature of −38 ° C.

(24-2. Production of binder composition for secondary battery)
In a container, add the aqueous dispersion of the particulate polymer prepared in (24-1) above in an amount corresponding to a solid content of 95 parts and 0.25 parts of sodium dioctylsulfosuccinate, and then mix. An aqueous solution of the water-soluble polymer prepared in (1-1) of Example 1 was added to an amount corresponding to 5 parts in terms of solid content, and water was added and mixed to form a binder composition for a secondary battery having a solid content concentration of 25%. I got a thing.
About this binder composition, the contact angle was measured by the method mentioned above.

(24-3. Preparation of slurry composition for porous membrane)
As non-conductive fine particles, alumina having a volume average particle diameter D50 of 0.5 μm (product name: AKP-3000, manufactured by Sumitomo Chemical Co., Ltd.) was prepared. In addition, acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer sodium salt (product name: Aron A-6020, manufactured by Toagosei Co., Ltd.) was prepared as a dispersant. Further, carboxymethyl cellulose (average polymerization degree 500 to 600, etherification degree 0.8 to 1.0, manufactured by Daicel Chemical Industries, product name Daicel 1220) was dissolved in ion-exchanged water as a viscosity modifier, and 5% An aqueous solution was prepared.
To 100 parts of non-conductive fine particles, in terms of solid content, 0.5 part of the dispersant, 6 parts of the binder composition for secondary battery obtained in (24-2), and a viscosity modifier The mixture was mixed so that the solid content was 1.5 parts, and further mixed so that the solid content concentration of the final slurry was 40% by mass, and dispersed using a bead mill to produce a slurry composition for a porous membrane. .

(24-4. Preparation of separator with porous membrane)
A separator base material made of a polypropylene porous base material (manufactured by Celgard, product name 2500, thickness 25 μm) was prepared. The slurry composition for porous membrane obtained in (24-3) is applied to one side of the prepared separator substrate, dried at 60 ° C. for 10 minutes to form a porous membrane layer, and the separator substrate and the porous membrane layer are A separator with a porous film having a thickness of 29 μm was obtained. This was cut into a 5 × 5 cm ² square to obtain a square separator.

(24-5. Lithium ion secondary battery)
An aluminum packaging exterior was prepared as the battery exterior. The positive electrode obtained in (1-7) of Example 1 was cut into a square of 4.6 × 4.6 cm ² to obtain a square positive electrode. This square positive electrode was placed so that the current collector-side surface was in contact with the aluminum packaging exterior. On the surface of the square positive electrode on the positive electrode active material layer side, the square separator obtained in (24-4) above was placed. The square separator was disposed with the surface on the porous membrane layer side facing the square positive electrode side.
The negative electrode after pressing obtained in (20-4) of Example 20 was cut into a 5 × 5 cm ² square to obtain a square negative electrode. This square negative electrode was placed on a square separator so that the surface on the negative electrode active material layer side faces the separator. An electrolyte solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 volume ratio (25 ° C.), electrolyte: LiPF _{6 at a} concentration of 1 M) was injected so that no air remained, and further, 150 ° C. The aluminum exterior was closed by heat sealing, and the opening of the aluminum packaging was sealed. Thereby, the lithium ion secondary battery was manufactured. About the obtained lithium ion secondary battery, the low temperature acceptance characteristic, the low temperature output characteristic, and the cycle characteristic were evaluated by the method described above. However, the low temperature acceptance property was evaluated for the separator.

<Comparative Example 1>
(C1-1. Production of binder composition for secondary battery)
In a container, an amount of the aqueous dispersion of the particulate polymer prepared in (1-2) of Example 1 in an amount corresponding to 100 parts in solid content, 11 parts of sodium dioctylsulfosuccinate, and water are mixed and mixed. A binder composition for a secondary battery having a solid content concentration of 25% was obtained.
About this binder composition, the contact angle was measured by the method mentioned above.

(C1-2. Lithium ion secondary battery)
Except for the following points, lithium ion secondary batteries were produced and evaluated in the same manner as (1-4) to (1-9) of Example 1.
In the production of the negative electrode slurry composition of (1-4), instead of the binder composition for secondary battery of (1-3) in Example 1, the binder composition for secondary battery of (C1-1) above. Things were used.

<Comparative example 2>
(C2-1. Production of water-soluble polymer)
In a 5 MPa pressure vessel with a stirrer, 80 parts of methacrylic acid (acidic functional group-containing monomer), 19.0 parts of ethyl acrylate (other monomer), polyoxyalkylene alkenyl ether ammonium sulfate as a reactive surfactant (Kao Corporation) "Latemul PD-104" manufactured by company, 1.0 part, 0.6 part of t-dodecyl mercaptan, 150 parts of ion-exchanged water, and 1.0 part of potassium persulfate (polymerization initiator) were added and thoroughly stirred. The polymerization was started by heating to 60 ° C. When the polymerization conversion reached 96%, the reaction was stopped by cooling to obtain a mixture containing a water-soluble polymer. 10% aqueous ammonia was added to the mixture containing the water-soluble polymer to adjust the pH to 8 to obtain an aqueous solution containing the desired water-soluble polymer.
A part of the obtained aqueous solution containing the water-soluble polymer was taken, water was added to make a 1% aqueous solution, and this was used as a sample to measure the viscosity. As a result, it was 250 mPa · s.

(C2-2. Production of binder composition for secondary battery)
An amount of the aqueous dispersion of the particulate polymer prepared in (1-2) of Example 1 in an amount of 95 parts by solid content, an aqueous solution of the water-soluble polymer prepared in (C2-1) above. Was added in an amount corresponding to 5 parts in solid content, and water was mixed to obtain a secondary battery binder composition having a solid content concentration of 25%.
About this binder composition, the contact angle was measured by the method mentioned above.

(C2-3. Lithium ion secondary battery)
Except for the following points, lithium ion secondary batteries were produced and evaluated in the same manner as (1-4) to (1-9) of Example 1.
In the production of the negative electrode slurry composition of (1-4), instead of the secondary battery binder composition of (1-3) of Example 1, the secondary battery binder composition of (C2-2) above. Things were used.

<Comparative Example 3>
(C3-1. Production of water-soluble polymer)
In a 5 MPa pressure vessel with a stirrer, 80 parts of methacrylic acid (acidic functional group-containing monomer), 19.0 parts of ethyl acrylate (other monomer), polyoxyalkylene alkenyl ether ammonium sulfate as a reactive surfactant (Kao Corporation) "Latemul PD-104" manufactured by company, 1.0 part, 0.6 part of t-dodecyl mercaptan, 150 parts of ion-exchanged water, and 1.0 part of potassium persulfate (polymerization initiator) were added and thoroughly stirred. The polymerization was started by heating to 60 ° C. When the polymerization conversion reached 96%, the reaction was stopped by cooling to obtain a mixture containing a water-soluble polymer. 10% aqueous ammonia was added to the mixture containing the water-soluble polymer to adjust the pH to 8 to obtain an aqueous solution containing the desired water-soluble polymer.
A part of the obtained aqueous solution containing the water-soluble polymer was taken, water was added to make a 1% aqueous solution, and this was used as a sample to measure the viscosity. As a result, it was 250 mPa · s.

(C3-2. Production of binder composition for secondary battery)
An amount of the aqueous dispersion of the particulate polymer prepared in (20-1) of Example 20 in an amount of 95 parts by solid content, an aqueous solution of the water-soluble polymer prepared in (C3-1) above. Was added in an amount corresponding to 5 parts in solid content, and water was mixed to obtain a secondary battery binder composition having a solid content concentration of 25%.
About this binder composition, the contact angle was measured by the method mentioned above.

(C3-3. Lithium ion secondary battery)
A lithium ion secondary battery was produced and evaluated in the same manner as in (20-3) to (20-8) of Example 20 except for the following points.
In the production of the positive electrode slurry composition of (20-5), instead of the secondary battery binder composition of (20-2) of Example 20, the secondary battery binder composition of (C3-2) above. Things were used.

<Comparative Example 4>
(C4-1. Production of water-soluble polymer)
In a 5 MPa pressure vessel with a stirrer, 32.5 parts of methacrylic acid (acidic functional group-containing monomer), 7.5 parts of 2,2,2-trifluoroethyl methacrylate (fluorine-containing (meth) acrylic acid ester monomer) , Ethyl acrylate (other monomers) 58.2 parts, ethylene dimethacrylate (crosslinkable monomer) 0.8 parts, polyoxyalkylene alkenyl ether ammonium sulfate as a reactive surfactant (Latemul PD manufactured by Kao Corporation) -104 ") 1.0 part, 0.6 part of t-dodecyl mercaptan, 150 parts of ion-exchanged water, and 1.0 part of potassium persulfate (polymerization initiator), and after stirring sufficiently, the mixture was heated to 60 ° C. The polymerization was started by warming. When the polymerization conversion reached 96%, the reaction was stopped by cooling to obtain a mixture containing a water-soluble polymer. 10% aqueous ammonia was added to the mixture containing the water-soluble polymer to adjust the pH to 8 to obtain an aqueous solution containing the desired water-soluble polymer.
A part of the obtained aqueous solution containing the water-soluble polymer was taken, water was added to make a 1% aqueous solution, and this was used as a sample to measure the viscosity. As a result, it was 68 mPa · s.

(C4-2. Production of secondary battery binder composition)
An amount of the aqueous dispersion of the particulate polymer prepared in (24-1) of Example 24 in an amount of 95 parts by solid content, an aqueous solution of the water-soluble polymer prepared in (C4-1) above. Was added in an amount corresponding to 5 parts in solid content, and water was mixed to obtain a secondary battery binder composition having a solid content concentration of 25%.
About this binder composition, the contact angle was measured by the method mentioned above.

(C4-3. Lithium ion secondary battery)
Except for the following points, lithium ion secondary batteries were produced and evaluated in the same manner as in (24-3) to (24-5) of Example 24.
In the production of the slurry composition for porous membrane of (24-3), the binder for secondary battery of (C4-2) is used instead of the binder composition for secondary battery of (24-2) of Example 24. The composition was used.

<Result>
The results of Examples and Comparative Examples described above are shown in Tables 1 to 4 below.

The meanings of the abbreviations in the above table are as follows.
Positive electrode / negative electrode: type of electrode or separator to which the binder composition of the present invention (in the comparative example, a control binder composition) is applied. Body type and quantity (parts). MAA: methacrylic acid, AMPS: 2-acrylamido-2-methylpropanesulfonic acid, AA: acrylic acid.
Type of F monomer: Type of fluorine-containing (meth) acrylic acid ester monomer used for the production of the water-soluble polymer. 2,2,2-TFEMA: 2,2,2-trifluoroethyl methacrylate, PFOA: perfluorooctyl acrylate, PFEA: perfluoroethyl acrylate.
F monomer amount: Amount (parts) of fluorine-containing (meth) acrylate monomer used in the production of the water-soluble polymer
Viscosity of 1% aqueous solution: Viscosity of 1% aqueous solution of water-soluble polymer Sulfo type: Type of sulfosuccinic acid ester used in the production of the secondary battery binder composition. DOSSA Na: sodium dioctylsulfosuccinate, DCHSSA Na: sodium dicyclohexylsulfosuccinate, DASSA Na: sodium diamylsulfosuccinate, DOSSA Li: lithium dioctylsulfosuccinate, DOSSA K: potassium dioctylsulfosuccinate.
Amount of sulfo: Amount (parts) of sulfosuccinate used in the production of the binder composition for secondary batteries.
Particle: Water: Ratio of the particulate polymer and the water-soluble polymer used in the production of the secondary battery binder composition.
Active material: The type of electrode active material. LCO: LiCoO ₂ , LFP: LiFePO ₄ , NMC: LiNi _0.8 Co _0.1 Mn _0.1 O ₂
Low-temperature acceptance: Ratio of the area where lithium metal is deposited to the area of the entire surface of one side of the negative electrode, positive electrode or separator measured in the evaluation of the low-temperature acceptance characteristics (%)
Contact angle: The contact angle (°) with the electrolyte measured for the binder composition
Low temperature output: Voltage change ΔV (mV) measured in evaluation of low temperature output characteristics.
Cycle: Capacity retention rate ΔC (%) measured in the evaluation of cycle characteristics.
* 1: Both positive and negative electrodes are rated A * 2: Positive electrode 32.5 / Negative electrode 37.5

[Consideration]
As is apparent from the results of Tables 1 to 4, in the examples satisfying the requirements of the present invention, compared to the comparative example, there are secondary batteries having good performance in a balanced manner in cycle characteristics, low-temperature output characteristics and other evaluations. Obtained. From this, it was confirmed that according to the present invention, a secondary battery having good performance can be realized.

Claims (17)

A particulate polymer, a water-soluble polymer, a sulfosuccinic acid ester or a salt thereof, and water,
The water-soluble polymer contains 20 to 70% by weight of acid group-containing monomer units,
The sulfosuccinic acid ester or a salt thereof is represented by the following formula (i):

(In the formula, each of R ¹ and R ² is independently selected from the group consisting of Na, K, Li, NH ₄ and an alkyl group having 1 to 12 carbon atoms, and X is Na, K, Li, and NH _4. Selected from the group consisting of:
The content ratio of the sulfosuccinic acid ester or a salt thereof is 0.01 to 10 parts by weight with respect to 100 parts by weight in total of the particulate polymer and the water-soluble polymer.
A binder composition for a lithium ion secondary battery.   The binder composition for a lithium ion secondary battery according to claim 1, wherein the water-soluble polymer further contains 0.1 to 30% by weight of a fluorine-containing monomer unit.   The binder composition for a lithium ion secondary battery according to claim 1 or 2, wherein the water-soluble polymer has a 1% aqueous solution viscosity of 1 to 1000 mPa · s.   The binder composition for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the water-soluble polymer further contains 0.1 to 2% by weight of a crosslinkable monomer unit.   The binder composition for a lithium ion secondary battery according to any one of claims 1 to 4, wherein the sulfosuccinic acid ester or a salt thereof is a dialkyl sulfosuccinic acid ester or a salt thereof. The lithium ion according to any one of claims 1 to 5 , wherein a quantitative ratio of the particulate polymer to the water-soluble polymer is particulate polymer / water-soluble polymer = 99/1 to 50/50. A binder composition for a secondary battery. The slurry composition for lithium ion secondary batteries containing the binder composition of any one of Claims 1-6 , and an electrode active material. Furthermore, the slurry composition for lithium ion secondary batteries of Claim 7 containing a thickener. The electrode for lithium ion secondary batteries formed by apply | coating the slurry composition for lithium ion secondary batteries of Claim 7 or 8 on a collector, and drying. A positive electrode, a negative electrode, and an electrolyte solution;
The lithium ion secondary battery whose said positive electrode, the said negative electrode, or both are the electrodes for lithium ion secondary batteries of Claim 9 . A particulate polymer, a water-soluble polymer, a sulfosuccinic acid ester or a salt thereof, and water, and the water-soluble polymer contains 20 to 70% by weight of an acid group-containing monomer unit, and the sulfosuccinic acid ester or a salt thereof The method for producing a binder composition for a lithium ion secondary battery , wherein the salt content is 0.01 to 10 parts by weight with respect to 100 parts by weight of the total of the particulate polymer and the water-soluble polymer ,
A step (1) of obtaining a mixture (1) by mixing a particulate polymer, a sulfosuccinic acid ester or a salt thereof, and water, and 20 to 70% by weight of the mixture (1) and an acid group-containing monomer unit. A water-soluble polymer is mixed, and the content ratio of the sulfosuccinic acid ester or salt thereof is 0.01 to 10 parts by weight with respect to 100 parts by weight in total of the particulate polymer and the water-soluble polymer ( 2) obtaining step (2)
Manufacturing method.   The production method according to claim 11, wherein the water-soluble polymer further contains 0.1 to 30% by weight of a fluorine-containing monomer unit.   The manufacturing method according to claim 11 or 12, wherein the water-soluble polymer has a 1% aqueous solution viscosity of 1 to 1000 mPa · s.   The method according to any one of claims 11 to 13, wherein the water-soluble polymer further contains 0.1 to 2% by weight of a crosslinkable monomer unit.   The production method according to any one of claims 11 to 14, wherein the sulfosuccinic acid ester or a salt thereof is a dialkyl sulfosuccinic acid ester or a salt thereof.   The sulfosuccinic acid ester or a salt thereof is represented by the following formula (i):

(Wherein R ¹ And R ² Are independently Na, K, Li, NH ₄ And an alkyl group having 1 to 12 carbon atoms, wherein X is Na, K, Li and NH ₄ The production method according to any one of claims 11 to 15, which is a compound represented by the formula (1) selected from the group consisting of:   The production method according to any one of claims 11 to 16, wherein a quantitative ratio of the particulate polymer to the water-soluble polymer is particulate polymer / water-soluble polymer = 99/1 to 50/50. .