KR102486608B1 - Polymer composition for non-aqueous secondary battery and non-aqueous secondary battery - Google Patents

Abstract

[Problem] To provide a polymer composition for a non-aqueous secondary battery and a non-aqueous secondary battery capable of exhibiting good cycle characteristics and initial capacity.
[Solution]
A polymer composition for a non-aqueous secondary battery containing polymer particles,
The Young's modulus of the polymer particles is 1.5 GPa or less,
The elastic deformation rate of the polymer particles is 50% or less,
The polymer composition for a non-aqueous secondary battery in which the swelling degree of the polymer particle is 1.5 times or less in an electrolyte solution.

Description

Polymer composition for non-aqueous secondary battery and non-aqueous secondary battery

The present invention relates to a polymer composition for a non-aqueous secondary battery and a non-aqueous secondary battery.

Conventionally, as a method for manufacturing an electrode used in an electrochemical device such as a lithium ion secondary battery, a liquid composition in which a binder or a thickener is added to an electrode active material is applied to the surface of a current collector and dried, on the current collector. A method of forming an electrode layer is exemplified. Here, styrene-butadiene-based copolymer latex is known as a binder capable of forming an electrode layer having high adhesion to the metal constituting the current collector and also having high flexibility. Further, the binder functions to improve adhesion between the electrode layer containing the active material and the current collector or separator, but the copolymer latex described above may have insufficient adhesion to the current collector or separator. If the adhesion is not sufficient, the charge/discharge cycle characteristics of the secondary battery tend to be impaired.

In view of the above, in Patent Document 1, a particulate polymer having a core cell structure formed of a polymer capable of swelling with an electrolyte solution at a predetermined swelling degree and having a core portion and a cell portion partially covering the outer surface of the core portion It is proposed to use as a binder.

Japanese Patent Publication No. 6436078

According to the binder described in Patent Literature 1, a lithium ion secondary battery having excellent adhesion in an electrolyte solution and excellent low-temperature output characteristics can be obtained. On the other hand, as a result of examination by the present inventors, in the core cell structure described in Patent Document 1, it has been found that the barrier properties of the cell portion are not sufficient, and as a result, there is still room for improvement in suppression of swelling in the electrolyte solution. In addition, suppression of swelling in an electrolyte solution and securing of flexibility are usually in a trade-off relationship, and according to the technique described in Patent Literature 1, it is difficult to achieve both these physical properties at a high level.

The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to provide a polymer composition for a non-aqueous secondary battery and a non-aqueous secondary battery capable of exhibiting good cycle characteristics and initial capacity.

As a result of intensive research, the inventors of the present invention have found that the above objects can be achieved by using polymer particles having predetermined physical properties, and have completed the present invention.

That is, the present invention includes the following aspects.

[One]

A polymer composition for a non-aqueous secondary battery containing polymer particles,

The Young's modulus of the polymer particles is 1.5 GPa or less,

The elastic deformation rate of the polymer particles is 50% or less,

The polymer composition for a non-aqueous secondary battery in which the swelling degree of the polymer particle is 1.5 times or less in an electrolyte solution.

[2]

The polymer particle has a core cell structure composed of a core portion and a cell portion,

The polymer composition for non-aqueous secondary batteries according to [1], wherein the core portion has a Young's modulus of 0.1 GPa or less.

[3]

The polymer composition for non-aqueous secondary batteries according to [2], wherein the swelling degree of the cell portion is 1.10 times or less.

[4]

When the total ethylenic monomers constituting the core cell structure are 100 mass%, the core portion contains ethylenically unsaturated carboxylic acid esters of 40 mass% or more and 80 mass% or less, and the cell portion is 15 mass% or more 60 Containing an ethylenically unsaturated carboxylic acid or an alkali metal salt thereof at 0% by mass or less and an ethylenically unsaturated monomer containing an N atom at 0% by mass or more and 45% by mass or less,

In [2] or [3], which contains 0.1 part by mass or less of an alkylene oxide structure and 0.3 part by mass or less of a sulfonic acid or a salt thereof, based on 100 parts by mass of all ethylenic monomers constituting the core cell structure. Polymer composition for non-aqueous secondary battery described.

[5]

Any one of [2] to [4], wherein the cell portion contains an N-atom-containing ethylenically unsaturated monomer of 15 mass% or more and 30 mass% or less when the total ethylenic monomers constituting the core cell structure is 100 mass%. The polymer composition for non-aqueous secondary batteries described in one.

[6]

The polymer composition for nonaqueous secondary batteries according to any one of [1] to [5], wherein the maximum value of the glass transition temperature of the polymer particles measured by DSC is 20°C or lower.

[7]

The polymer composition for non-aqueous secondary batteries according to any one of [1] to [6], wherein the average particle diameter of the polymer particles is 50 nm or more and 800 nm or less.

[8]

The polymer composition for non-aqueous secondary batteries according to any one of [2] to [7], wherein the mass ratio of the core portion in the core cell structure is 0.4 or more and 0.8 or less.

[9]

The polymer composition for non-aqueous secondary batteries according to any one of [1] to [8], further containing an isothiazoline-based compound of 0.0001 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the polymer particles.

[10] A nonaqueous secondary battery containing the polymer composition for a nonaqueous secondary battery according to any one of [1] to [9].

According to the present invention, it is possible to provide a polymer composition for a non-aqueous secondary battery and a non-aqueous secondary battery capable of exhibiting good cycle characteristics and initial capacity.

Hereinafter, an embodiment of the present invention (hereinafter also referred to as "this embodiment") will be described in detail. In addition, this invention is not limited to this embodiment below, It can implement with various modifications within the scope of the summary.

[Polymer composition for non-aqueous secondary battery]

The polymer composition for non-aqueous secondary batteries of the present embodiment (hereinafter also referred to as "the composition of the present embodiment") is a polymer composition for non-aqueous secondary batteries containing polymer particles, wherein the polymer particles have a Young's modulus of 1.5 GPa or less, The elastic deformation rate of the polymer particles is 50% or less, and the degree of swelling of the polymer particles in the electrolyte solution is 1.5 times or less. Since it is structured in this way, the composition of this embodiment can express favorable battery characteristics while being excellent in handleability.

(Physical properties of polymer particles)

The polymer particles in this embodiment have a Young's modulus of 1.5 GPa or less. Here, the Young's modulus becomes an index for evaluating the flexibility of polymer particles, and when the value is 1.5 GPa or less, the flexibility becomes excellent. From this point of view, the Young's modulus is preferably 1.3 GPa or less, and more preferably 1.0 GPa or less.

The Young's modulus can be measured by the method described in Examples described later.

In addition, the Young's modulus can be adjusted within the above range by, for example, containing a preferable monomer component described later in a preferable amount as a constituent component of the polymer particle.

The elastic deformation rate of the polymer particle in this embodiment is 50% or less. Here, the elastic deformation work rate is an index for evaluating the recovery ability of polymer particles against deformation, and when the value is 50% or less, it contributes to stress relaxation. From this point of view, the elastic deformation rate is preferably 45% or less, more preferably 40% or less.

The elastic deformation work rate can be measured by the method described in Examples described later.

Moreover, the elastic deformation rate can be adjusted to the said range by containing the suitable monomeric component mentioned later in a suitable amount as a structural component of a polymer particle, etc.

The polymer particle in this embodiment has an electrolyte solution swelling degree of 1.5 times or less. Here, the electrolyte solution swelling degree becomes an index for evaluating the resistance of the polymer particles to the electrolyte solution, and when the value is 1.5 times or less, adhesion to the current collector or the separator can be maintained even in the electrolyte solution. From this point of view, the electrolyte solution swelling degree is preferably 1.3 times or less, and more preferably 1.2 times or less.

The degree of swelling of the electrolyte solution can be measured by the method described in Examples described later.

Moreover, the degree of swelling of the electrolyte solution can be adjusted within the above range by containing a preferable amount of a preferable monomer component described later as a constituent component of the polymer particle.

As described above, since the Young's modulus, the elastic deformation rate, and the degree of swelling of the electrolyte solution of the polymer particles in the present embodiment satisfy a predetermined range, suppression of swelling in the electrolyte solution and securing of flexibility, which have conventionally been in a trade-off relationship, can be achieved. They are compatible, and therefore, the composition of the present embodiment can exhibit good battery characteristics while being excellent in handleability.

It is preferable that the polymer particle in this embodiment has a core cell structure containing a core part and a shell part. By having such a structure, the polymer particle in this embodiment becomes easy to ensure desired physical properties in this embodiment.

In this embodiment, the Young's modulus of the core portion is preferably 0.1 GPa or less, more preferably 0.07 GPa or less, still more preferably 0.04 GPa or less, from the viewpoint of further improving the flexibility of the polymer particles.

As described above, in the core portion of the polymer particle in the present embodiment, when the Young's modulus satisfies a predetermined range, the stress relaxation tends to be more excellent.

The Young's modulus of the core portion can be measured by the method described in Examples described later.

In addition, the Young's modulus of the core portion can be adjusted within the above range by containing a preferable monomer component described later in a preferable amount as a constituent component of the polymer particle.

In the present embodiment, from the viewpoint of improving the resistance to the electrolyte solution, the swelling degree of the cell portion is preferably 1.10 times or less, more preferably 1.05 times or less, still more preferably 1.01 times or less.

The electrolyte solution swelling degree of the cell portion can be measured by the method described in Examples described later.

In addition, the degree of swelling of the electrolyte solution of the cell portion can be adjusted within the above range by containing a preferable monomer component described later in a preferable amount as a constituent component of the polymer particle.

From the viewpoint of further enhancing flexibility, the polymer particles in the present embodiment preferably have a maximum glass transition temperature of the polymer particles measured by DSC of 20°C or less, more preferably 10°C or less, and still more preferably is below 0 °C.

Further, in the present embodiment, from the viewpoint of further enhancing the flexibility of the polymer particles, the maximum value of the glass transition temperature of the core portion is preferably 20°C or less, more preferably 10°C or less, still more preferably 0°C or less. to be.

Further, in the present embodiment, from the viewpoint of improving reliability under high temperature, the minimum glass transition temperature of the cell portion is preferably 200°C or higher, more preferably 250°C or higher, still more preferably 300°C or higher. to be.

Each of the glass transition temperatures described above can be measured by the method described in Examples described later, and can be adjusted to the above ranges, respectively, by containing a preferable amount of a preferable monomer component described later as a constituent component of the polymer particle.

From the viewpoint of contributing to stress relaxation, the polymer particles in the present embodiment preferably have an average particle diameter of 50 nm or more and 800 nm or less, more preferably 100 nm or more and 700 nm or less, and still more preferably 200 nm It is more than 600 nm or less.

The average particle size described above can be measured by the method described in Examples described later, and can be adjusted within the above ranges, respectively, by the monomer composition ratio of the constituent components of the polymer particle, the polymerization temperature, the emulsifier, and the like.

Regarding the core cell structure in the present embodiment, from the viewpoint of improving the balance of swelling suppression and flexibility in the electrolyte solution, the mass ratio of the core portion is preferably 0.40 or more and 0.80 or less, more preferably 0.45 or more and 0.75 or less. , and more preferably 0.50 or more and 0.70 or less.

The mass ratio described above can be measured by the method described in Examples described later, and can be adjusted within the above ranges, respectively, by the compounding ratio of the monomer components of the polymer particles and the like.

(Composition of Polymer Particles)

From the viewpoint of adjusting the Young's modulus, the elastic deformation rate, and the degree of swelling of the electrolyte solution to a preferred range, the polymer particles in the present embodiment have a core portion of 40% when all ethylenic monomers constituting the core cell structure are 100% by mass. An ethylenically unsaturated carboxylic acid or an alkali metal salt thereof containing an ethylenically unsaturated carboxylic acid ester of 80% by mass or more and having a cell portion of 15% by mass or more and 60% by mass or less, and 0% by mass or more and 45% by mass or less containing an N atom-containing ethylenically unsaturated monomer, and 0.1 part by mass or less of an alkylene oxide structure and 0.3 part by mass or less of a sulfonic acid or salt thereof, based on 100 parts by mass of all ethylenic monomers constituting the core-cell structure. It is preferable to contain.

The content of each unit can be specified by analyzing the polymer particles by a conventional method, but can also be specified as a preparation ratio of each monomer.

Hereinafter, the content of each unit is explained in detail.

In the present embodiment, from the viewpoint of contributing to stress relaxation more, when the total ethylenic monomers constituting the core cell structure are 100 mass%, the core portion is 40 mass% or more and 80 mass% or less Ethylenically unsaturated carboxylic acid ester It is preferable to contain, More preferably, it is 45 mass % or more and 75 mass % or less, More preferably, it is 50 mass % or more and 70 mass % or less.

In the present embodiment, 100% by mass of all ethylenic monomers constituting the core cell structure from the viewpoints of further suppressing swelling in the electrolyte solution, improving cycle characteristics, and further enhancing adhesion to other members. It is preferable that the cell portion contains 15 mass% or more and 60 mass% or less of an ethylenically unsaturated carboxylic acid or an alkali metal salt thereof, more preferably 18 mass% or more and 50 mass% or less, still more preferably 20 It is mass % or more and 40 mass % or less.

In the present embodiment, from the viewpoint of further suppressing swelling in the electrolyte solution and improving the cycle characteristics, when the total ethylenic monomers constituting the core cell structure are 100 mass%, the cell portion is 0 mass% or more It is preferable to contain an ethylenically unsaturated monomer containing an N atom of 45% by mass or less, more preferably 10% by mass or more and 30% by mass or less, still more preferably 20% by mass or more and 25% by mass or less.

In the present embodiment, the content of the alkylene oxide structure is 0.1 part by mass or less when the total ethylenic monomers constituting the core cell structure are 100 parts by mass from the viewpoint of improving the defoaming property and making the composition more excellent in handling. It is preferable, more preferably 0.08 part by mass or less, still more preferably 0.05 part by mass or less. As content of an alkylene oxide structure, the one with less is preferable, and although the lower limit is not specifically limited, For example, you may contain 0.02 mass part, and may contain 0.01 mass part. From the same viewpoint, the content of sulfonic acid or its salt is preferably 0.3 parts by mass or less, more preferably 0.2 parts by mass or less, and still more preferably 0.1 below the mass part. As content of sulfonic acid or its salt, the one with less is preferable, and the lower limit is not specifically limited, For example, you may contain 0.05 mass part, and may contain 0.03 mass part.

Although it does not specifically limit as a monomer (raw material monomer) which comprises the polymer particle in this embodiment, For example, ethylenically unsaturated carboxylic acid ester, ethylenically unsaturated carboxylic acid or its alkali metal salt, N-atom containing ethylene sexually unsaturated monomers and monomers copolymerizable with them, which may be present in either the core portion or the shell portion; It is preferable to use an ethylenically unsaturated carboxylic acid or an alkali metal salt thereof and an ethylenically unsaturated monomer containing an N atom as raw material monomers constituting the cell portion.

Although it does not specifically limit as an ethylenically unsaturated carboxylic acid ester, For example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate , n-butyl(meth)acrylate, i-butyl(meth)acrylate, n-amyl(meth)acrylate, i-amyl(meth)acrylate, hexyl(meth)acrylate, 2-hexyl(meth)acrylate Acrylates, octyl(meth)acrylate, i-nonyl(meth)acrylate, decyl(meth)acrylate, 2-ethylhexylacrylate, hydroxymethyl(meth)acrylate, hydroxyethyl(meth)acrylate etc. can be mentioned. These can be used individually by 1 type or in combination of 2 or more types.

Among the above, from the viewpoint of flexibility, it is preferable to use an ethylenically unsaturated carboxylic acid ester having a glass transition temperature of 20 ° C. or less when made into a homopolymer, and also from the viewpoint of adjusting the elastic deformation work rate to a preferable range, single tube It is preferable to use a functional ethylenically unsaturated carboxylic acid ester. In this embodiment, considering the stability of the polymer particles, ethyl acrylate is particularly preferred.

Although it does not specifically limit as an ethylenic unsaturated carboxylic acid, For example, fumaric acid, itaconic acid, acrylic acid, methacrylic acid, etc. are mentioned. These can be used individually by 1 type or in combination of 2 or more types.

Among the above, methacrylic acid is preferable from the viewpoint of the stability of the polymer particles.

Examples of the N atom-containing ethylenically unsaturated monomer include, but are not particularly limited to, aminoethyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, 2-vinylpyridine, 4-vinylpyridine acrylamide, acrylamide, meta Crylamide, N-methylol acrylamide, glycidyl methacrylamide, N,N-butoxymethyl acrylamide, etc. are mentioned. These can be used individually by 1 type or in combination of 2 or more types.

Among the above, acrylamide and methacrylamide are preferable from the viewpoint of the stability of the polymer particles.

Although it does not specifically limit as a monomer copolymerizable with the above-mentioned monomer, For example, an aromatic vinyl compound, a vinyl cyanide compound, etc. are mentioned.

Examples of the aromatic vinyl compound include, but are not particularly limited to, styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, and divinylbenzene. Can be used in combination.

Examples of the vinyl cyanide compound include, but are not particularly limited to, acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile. These monomers are used alone or in combination of two or more. and can be used.

(purpose)

The composition of this embodiment may contain various well-known arbitrary components other than the polymer particle in this embodiment, depending on the use. The use of the composition of the present embodiment is not particularly limited as long as it is used as a material for a non-aqueous secondary battery, and it can be used as a material for a negative electrode, a material for a positive electrode, a material for a separator, and the like. particularly preferred.

Hereinafter, when using the composition of this embodiment for manufacture of a negative electrode, a positive electrode, or a separator, it shall be called especially "the composition for battery material manufacture." Here, when manufacturing a negative electrode with the composition for battery material manufacture, the composition for battery material manufacture can contain the polymer particle in this embodiment, the negative electrode active material, and arbitrary components as needed. Moreover, when manufacturing a positive electrode with the composition for battery material manufacture, the composition for battery material manufacture can contain the polymer particle in this embodiment, the positive electrode active material, and arbitrary components as needed. In addition, when manufacturing a separator with the composition for battery material manufacture, the composition for battery material manufacture can contain the polymer particle in this embodiment, the separator raw material, and arbitrary components as needed.

On the other hand, when the composition of the present embodiment does not contain any of the negative electrode active material, the positive electrode active material, and the separator raw material, it can be applied as an additive for battery material production. In other words, when the composition of the present embodiment is used for binder applications, it is referred to as "binder composition", and when used for thickener applications, it is referred to as "thickener composition".

As described above, the term "composition of the present embodiment" can be said to include "composition for battery material production", "composition for binder" and "composition for thickener", and in any application, the present embodiment It is common in the point that the polymer particle in is contained. Moreover, in any use, when the composition of this embodiment contains an arbitrary component, the kind, blending ratio, etc. are not specifically limited, What is necessary is just to decide suitably according to a use.

Although it does not specifically limit as a negative electrode active material which can be used when manufacturing a negative electrode with the composition for battery material manufacture, For example, a carbon-type active material and a silicon-type active material are mentioned.

Examples of the carbon-based active material include, but are not particularly limited to, graphite, carbon fiber, coke, hard carbon, mesocarbon microbeads (MCMB), furfuryl alcohol resin fired body (PFA), and conductive polymers (poly-p- phenylene, etc.) and the like.

Although it does not specifically limit as a silicon type active material, For example, silicon, SiOx (0.01<= _x <2), the alloy of silicon and a transition metal, etc. are mentioned.

In the case of producing a positive electrode with the composition for producing a battery material, the positive electrode active material that can be used is not particularly limited, and examples thereof include lithium-containing composite oxides, transition metal oxides, transition metal fluorides, and transition metal sulfides. .

Examples of the lithium-containing composite oxide include, but are not particularly limited to, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiXCoYSnZO ₂ , LiFePO ₄ , LiXCoYSnZO ₂ and the like.

Examples of the transition metal oxide include, but are not particularly limited to, MnO ₂ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ , Fe ₂ O ₃ , Fe ₃ O ₄ and the like.

Although it does not specifically limit as _a transition metal fluoride, For example, CuF2, _NiF2 etc. are mentioned.

Although it does not specifically limit as a transition metal sulfide, For example, _TiS2 , _TiS3 , _MoS3 , _FeS2 etc. are mentioned.

In this embodiment, it is preferable that the composition for binders contains the polymer particle in this embodiment and 0.0001 mass part or more and 1.0 mass part or less of an isothiazoline type compound with respect to 100 mass parts of the said polymer particle. When the above range is satisfied, viscosity behavior, which is hysteresis against shear force, can be suppressed, and more stable coating properties tend to be exhibited. The isothiazoline-based compound is not particularly limited, and various known compounds can be employed, and examples thereof include 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4. -Isothiazolin-3-one, 1,2-benzoisothiazolin-3-one, 2-n-octyl 4-isothiazolin-3-one, 4,5-dichloro-2-n-octyl-4 -Isothiazolin-3-one, 2-ethyl-4-isothiazolin-3-one, 4,5-dichloro-2-cyclohexyl-4-isothiazolin-3-one, 5-chloro-2- Ethyl-4-isothiazolin-3-one, 5-chloro-2-t-octyl-4-isothiazolin-3-one, 4-chloro-2-n-octyl-4-isothiazoline-3- one, 5-chloro-2-n-octyl-4-isothiazolin-3-one, N-n-butyl-1,2-benzoisothiazolin-3-one, N-butylbenzoisothiazolin-3-one , N-methylbenzoisothiazolin-3-one, N-ethylbenzoisothiazolin-3-one, N-propylbenzoisothiazolin-3-one, N-isobutylbenzoisothiazolin-3-one, N-pentylbenzoisothiazolin-3-one, N-isopentylbenzoisothiazolin-3-one, N-hexylbenzoisothiazolin-3-one, N-allylbenzoisothiazolin-3-one, N - (2-butenyl) benzoisothiazolin-3-one etc. are mentioned. Among these, 2-methyl-4-isothiazolin-3-one is preferable.

In addition, the binder composition of the present embodiment may contain an antifoaming agent as an optional component.

Examples of the antifoaming agent include mineral oil-based, silicone-based, acrylic-based, and polyether-based various antifoaming agents. When an antifoaming agent is contained, there is a tendency for more excellent defoaming properties.

In this case, the type or blending ratio of the optional components is not particularly limited.

(Method for Producing Polymer Composition for Non-Aqueous Secondary Battery)

Although it does not specifically limit as a method for manufacturing the composition of this embodiment, It can manufacture suitably by the following manufacturing method (henceforth also referred to as "the manufacturing method of this embodiment"). That is, in order to obtain a composition containing polymer particles having a core cell structure, a method of performing emulsion polymerization using the above-described raw material monomers and the like is preferable. In polymerization, suitable sheet particles can be used, and sheet particles can also be obtained by ordinary emulsion polymerization. In addition, in the case of emulsion polymerization, a well-known method can be adopted, and it can manufacture by using a polymerization initiator, molecular weight modifier, chelating agent, pH adjuster, emulsifier, etc. suitably in an aqueous medium.

Although it does not specifically limit as an emulsifier, For example, anionic surfactant, a nonionic surfactant, an amphoteric surfactant, a reactive surfactant, etc. can be used individually or in combination of 2 or more types.

Examples of the anionic surfactant include, but are not particularly limited to, sulfuric acid esters of higher alcohols, alkylbenzene sulfonic acid salts, aliphatic sulfonic acid salts, and polyethylene glycol alkyl ether sulfate esters.

Although it does not specifically limit as a nonionic surfactant, For example, the alkyl ester type of polyethylene glycol, the alkyl ether type, the alkylphenyl ether type, etc. are used.

Examples of the amphoteric surfactant include, but are not particularly limited to, betaines such as lauryl betaine and stearyl betaine, lauryl-β-alanine, stearyl-β-alanine, lauryl di(aminoethyl ) amino acid type such as glycine, etc. are used.

Although it does not specifically limit as a reactive surfactant, For example, polyoxyethylene alkyl propenylphenyl ether, α-[1-[(allyloxy) methyl] -2-(nonylphenoxy) ethyl] -ω-hydride Oxypolyoxyethylene etc. are mentioned.

The polymerization initiator is not particularly limited, but examples thereof include water-soluble polymerization initiators such as sodium persulfate, potassium persulfate, and ammonium persulfate, oil-soluble polymerization initiators such as benzoyl peroxide and lauryl peroxide, and combinations with reducing agents. A dox type polymerization initiator etc. can be used individually or in combination.

In the production method of the present embodiment, conditions such as stirring speed, polymerization temperature, and reaction (polymerization) time are not particularly limited as long as the composition of the present embodiment is obtained. Typically, the stirring speed can be usually 50 rpm or more and 500 rpm or less, the polymerization temperature can be usually 50 ° C. or more and 100 ° C. or less, and the reaction time can be usually 3 hours or more and 72 hours or less. there is.

In the production method of the present embodiment, after obtaining the polymer particles as described above, the composition of the present embodiment can be obtained by dispersing the polymer particles in a dispersion medium and adding optional components as necessary. Water can be used as a dispersion medium, and, if necessary, an organic solvent suitable for the active material can also be used.

(Non-aqueous secondary battery)

The non-aqueous secondary battery of this embodiment can be manufactured using the composition of this embodiment. In other words, the non-aqueous secondary battery of this embodiment contains the composition of this embodiment.

When the non-aqueous secondary battery of the present embodiment is a lithium ion secondary battery, typical constituent members thereof include a negative electrode, a negative electrode current collector, a positive electrode, a positive electrode current collector, a separator, and an electrolyte solution, and the non-aqueous secondary battery of the present embodiment In the battery, at least one of the main members (negative electrode, positive electrode, and separator) may be obtained by using the composition of the present embodiment, that is, at least one of the main members may contain the composition of the present embodiment.

Whether or not each member contains the composition of the present embodiment can be specified depending on whether or not the polymer particles in the present embodiment are contained in the member.

The manufacturing method of the non-aqueous secondary battery of the present embodiment is not particularly limited, but taking a lithium ion secondary battery as an example, the composition of the present embodiment is applied to a current collector, heated, and dried to form a corresponding electrode. and making the positive electrode and the negative electrode face each other through a separator, injecting an electrolyte solution, and sealing. The negative electrode current collector is not particularly limited, but, for example, copper foil is used, and the positive electrode current collector is not particularly limited, but aluminum foil is used, for example. Although it does not specifically limit as electrolyte solution, For example, what dissolved electrolyte, such as LiClO ₄ , LiBF ₄ , LiPF ₆ in an organic solvent, can be used. Examples of the organic solvent include, but are not particularly limited to, ethers, ketones, lactones, nitriles, amines, amides, carbonates, and chlorinated hydrocarbons. Typical examples include tetrahydrofuran, Acetonitrile, butyronitrile, propylene carbonate, ethylene carbonate, diethyl carbonate, etc. are mentioned, and it is used as 1 type or a mixture of 2 or more types.

The coating method is not particularly limited, and any coater head such as a reverse roll coater, a comma bar coater, a gravure coater, or an air knife coater can be used, for example. It is not specifically limited also as a drying method, For example, standing drying, blowing drying, warm air drying, an infrared heater, a far-infrared superheater, etc. can be used. The drying temperature is not particularly limited, and can be, for example, 60°C to 150°C.

Example

Although examples are given below to explain this embodiment more concretely, this embodiment is not limited at all by these Examples. For convenience of description, in the following examples, words such as "composition" and "coating liquid" are used, but all are concepts included in the composition of the present embodiment.

[Example 1]

Ion-exchanged water was added to the reactor, and the temperature was raised to 65°C and maintained while stirring. Here, after adding sodium persulfate (hereinafter also referred to as "NPS") as a polymerization initiator, methacrylic acid (hereinafter also referred to as "MAA") and methacrylic acid as monomers (hereinafter also referred to as "monomer") components A solution in which amide (hereinafter also referred to as “MAAm”) was dissolved in ion-exchanged water and a 10% aqueous solution of sodium hydroxide were added dropwise, and the addition was completed for 2 hours while maintaining the temperature at 65°C, and then polymerization was continued for 1 hour. . Then, ethyl acrylate (henceforth also referred to as "EA") was added dropwise, and polymerization was continued for 1 hour. As the compounding amount of each component at this time, when the total of monomer components (units derived from all ethylenically unsaturated monomers: EA, MAA, MAAm) is 100 parts by mass, EA is 80 parts by mass, MAA is 10 parts by mass, MAAm was blended at 10 parts by mass, and the blending amount of ion-exchanged water was 830 parts by mass.

Thereafter, the temperature was raised from 65°C to 80°C and maintained for 1.5 hours to complete polymerization.

Then, after adding 0.0005 parts by mass of 2-methyl-4-isothiazolin-3-one as an additive to 100 parts by mass of the obtained polymer particles, filtration was performed using a 200 μm mesh.

The obtained composition had a polymerization rate of 98%, pH 7, and solid content (polymer particles) of 9.8%. In addition, the polymerization rate was calculated by adding the solid content to the ratio of the amount of residue to the total amount of injected ingredients. Using this composition, a secondary battery negative electrode was prepared as follows. Specifically, it was manufactured as follows.

<Manufacture of coating solution for secondary battery negative electrode>

To 1.5 parts by mass of solid content of the obtained composition, 1.0 parts by mass of carboxymethylcellulose as a thickener component and 100 parts by mass of natural graphite as a negative electrode active material were further added, ion-exchanged water was added thereto, and the mixture was stirred with a mechanical stirrer. It was prepared so that the total solid content might be 60%. This was used as a premix, and then dispersed for 30 seconds at a peripheral speed of 20 m/sec using a thin film swirl type high-speed mixer (manufactured by PRIMIX, T.K. Fill Mix FM56-L type (product name)), followed by coating for secondary battery negative electrodes. made into a liquid.

<Manufacture of secondary battery negative electrode>

After applying the coating solution to one side of copper foil with a die coater so that the thickness after drying was 100 μm, it was dried at 60°C for 60 minutes. After drying at 120°C for 3 minutes, compression molding was performed with a roll press machine. The coating amount of the negative electrode active material was 106 g/m 2 , and the bulk density of the negative electrode active material was 1.35 g/cm 3 .

Using the composition obtained as described above and the secondary battery negative electrode, various physical property evaluations described later were performed. A result is shown in Table 1.

[Examples 2 to 10 and Comparative Examples 1 to 2]

In each case, the blending amounts of the monomer and 2-methyl-4-isothiazolin-3-one were changed as shown in Table 1.

In Example 5, as a monomer constituting the core, MAA was also added in a compounding amount shown in Table 1 at the timing of adding EA.

In Example 6, oxyethylene diacrylate was also added in a compounding amount shown in Table 1 at the timing of adding MAA and MAAm as monomers constituting the cell.

In Example 8, 2-methyl-4-isothiazolin-3-one was not added.

In Comparative Example 1, as a monomer constituting the core, methyl methacrylate (hereinafter also referred to as "MMA") was also added in a compounding amount shown in Table 1 at the timing of adding EA.

Except for the above points, in the same manner as in Example 1, the compositions of Examples 2 to 10 and Comparative Examples 1 to 2 were prepared to prepare a secondary battery negative electrode.

Using the composition obtained as described above and the secondary battery negative electrode, various physical property evaluations described later were performed. A result is shown in Table 1.

[Comparative Example 3]

In Comparative Example 3, with reference to Example I-5 of Patent Document 1 (Japanese Patent Publication No. 436078), a composition was prepared as follows to prepare a secondary battery negative electrode.

55 parts by mass of MMA, 20 parts by mass of 2-ethylhexyl acrylate (hereinafter also referred to as "2-EHA"), 4 parts by mass of MAA, and ethylene as monomer components used in the manufacture of the core portion in a 5 MPa pressure-resistant container with an agitator 1 part by mass of dimethacrylate (hereinafter, also referred to as "EDMA"); 1 part by mass of sodium dodecylbenzenesulfonate as an emulsifier; 150 parts by mass of ion-exchanged water and 0.5 parts by mass of potassium persulfate as a polymerization initiator were added, and the mixture was sufficiently stirred. Thereafter, polymerization was initiated by heating to 60°C. By continuing polymerization until the polymerization conversion ratio became 96%, an aqueous dispersion containing the particulate polymer constituting the core portion was obtained.

Then, this aqueous dispersion was heated to 70°C. To the aqueous dispersion, 20 parts by mass of styrene as a monomer used for producing the cell portion was continuously supplied over 30 minutes, and polymerization was continued. A composition containing polymer particles was prepared by cooling and stopping the reaction when the polymerization conversion ratio became 96%.

A secondary battery negative electrode was used in the same manner as in Example 1 except that the composition obtained as described above was used, and various physical property evaluations described later were performed. A result is shown in Table 1.

[Comparative Example 4]

In Comparative Example 4, with reference to Comparative Example I-4 of Patent Document 1 (Japanese Patent Publication No. 6436078), a composition was prepared as follows to prepare a secondary battery negative electrode.

A composition containing polymer particles was prepared in the same manner as in Comparative Example 3, except that 60 parts by mass of 2-EHA, 5 parts by mass of MAA, and 15 parts by mass of styrene were used as monomer components used for producing the core portion.

A negative electrode for a secondary battery was used in the same manner as in Example 1, except that the composition obtained as described above was used, and was subjected to various physical property evaluations described later. A result is shown in Table 1.

(average particle size)

The average particle diameter of the polymer particles was measured using a particle diameter measuring device (Microtrac UPA150 manufactured by Nikkiso Co., Ltd.). As the measurement conditions, the loading index = 0.15 to 0.3, the measurement time was 300 seconds, and the value of the 50% particle size in the obtained data was used as the average particle size by the dynamic light scattering method.

(Core Shelby and Cell Thickness)

Calculated by the following formula.

Core Shelby = Volume of Core/Volume of Polymer Particles x 100

In addition, the volume of a polymer particle was computed from the said average particle diameter. In addition, the volume of the core was calculated as follows from the cell thickness and average particle diameter estimated from the results of transmission electron microscope observation.

Core volume = {4π × (average particle diameter/2 - cell thickness) ＾3}/3

The cell thickness of the above formula was observed using a transmission electron microscope. A specific method is shown below.

After sufficiently dispersing the polymer particles in the thermosetting resin, they were embedded to prepare a block piece containing the polymer particles. Next, the block piece was cut out into thin pieces with a thickness of 100 nm using a microtome equipped with a diamond blade to prepare a sample for measurement. After that, the sample for measurement was dyed using ruthenium tetroxide.

Next, the dyed sample for measurement was set in a transmission electron microscope, and the cross-sectional structure of the polymer particles was photographed at an accelerating voltage of 80 kV. Magnification was set so that the cross section of one particulate polymer would fit into the magnification and field of view of the electron microscope.

From the cross-sectional structure of the observed polymer particles, the longest diameter of the polymer particles constituting the cell portion was measured. For 20 arbitrarily selected polymer particles, the longest diameter of the polymer particles constituting the cell part was measured by the above method, and the average of the longest diameters was taken as the cell thickness.

(electrolyte swelling degree)

The composition containing the polymer particles was left still in a 130°C oven for 1 hour and dried. The film of the polymer particles obtained by drying was cut into 0.5 g. The cut sample was put into a 50 ml vial bottle together with 10 g of a mixed solvent of ethylene carbonate : diethyl carbonate = 1 : 1 (mass ratio), and after permeating the mixed solvent at 60 ° C. for 1 day, the sample was taken out, and the above After washing with a mixed solvent, the mass (Wa: g) was measured. Then, after leaving the sample still in a 150 degreeC oven for 1 hour, the mass was measured (Wb:g), and the swelling degree with respect to the electrolyte solution of the copolymer was computed from the following formula.

Swelling degree (fold) of the polymer particles with respect to the electrolyte solution = (Wa - Wb)/(Wb)

In addition, about the electrolyte solution swelling degree of a cell part, it calculated as follows.

For Examples 1 to 5, Examples 7 to 10, and Comparative Examples 1 to 3, a polymer corresponding to the cell portion was prepared by the following method, and a film was formed in the same manner as above using the polymer, and evaluated. .

Ion-exchanged water was added to the reactor, and the temperature was raised to 65°C and maintained while stirring. After adding NPS as a polymerization initiator to this, a solution in which MAA and MAAm were dissolved in ion-exchanged water and a 10% aqueous sodium hydroxide solution were added dropwise as monomer components, and the dropwise addition was completed for 2 hours while maintaining the temperature at 65°C. After that, polymerization was continued for 1 hour.

The blending amount of each component at this time is 50 parts by mass of MAA and 50 parts by mass of MAAm when the total of monomer components (units derived from all ethylenically unsaturated monomers: MAA, MAAm) is 100 parts by mass, , The blending amount of ion-exchanged water was 830 parts by mass.

Thereafter, the temperature was raised from 65°C to 80°C and maintained for 1.5 hours to complete polymerization.

In Example 6, 20 parts by mass of oxyethylene diacrylate was further added as a monomer in the above polymer production method at the timing of adding MAA and MAAm.

Comparative Examples 4 and 5 were prepared by dissolving commercially available polystyrene in ethyl acetate.

(Young's modulus)

A mold having a width of 30 mm × length of 100 mm × height of 10 mm was installed on a smooth aluminum plate. 12 g of a composition (aqueous dispersion) containing polymer particles adjusted to a solid content of 5% was poured there. After drying this at room temperature for 24 hours, a 200-micrometer-thick film was obtained by drying at 100 degreeC for 1 hour. Using a micro durometer, the probe was pressed against the film at a load of 30 mN/20 s, and then held for 5 s. In addition, the indentation depth was evaluated by unloading under the same condition with increasing load. The Young's modulus was calculated from the obtained load-displacement curve.

In addition, the Young's modulus of the core portion was calculated as follows.

In Examples 1 to 4, Examples 6 to 10, and Comparative Example 2, a polymer corresponding to the core portion was prepared by the following method, a film adjusted to a thickness of 200 μm was prepared using the polymer, and the film was Evaluation was conducted in the same manner as above.

Ion-exchanged water was added to the reactor, and the temperature was raised to 65°C and maintained while stirring. After adding NPS as a polymerization initiator here, EA was added dropwise and polymerization was performed for 1 hour. As the compounding quantity of EA at this time, when the EA compounding quantity was 100 mass parts, the compounding quantity of ion-exchanged water was 830 mass parts.

Thereafter, the temperature was raised from 65°C to 80°C and maintained for 1.5 hours to complete polymerization.

In Example 5, as a monomer, 50 parts by mass of MAA was added at the timing of adding EA.

In Comparative Example 1, 100 parts by mass of MMA was added as a monomer at the timing of adding EA.

In Comparative Example 3, instead of 100 parts by mass of EA, 20 parts by mass of 2-EHA, 55 parts by mass of MMA, 4 parts by mass of MAA, and 1 part by mass of EDMA were added.

In Comparative Example 4, 60 parts by mass of 2-EHA, 5 parts by mass of MAA, and 15 parts by mass of styrene were added instead of 100 parts by mass of EA.

(elastic deformation rate)

A mold having a width of 30 mm × length of 100 mm × height of 10 mm was installed on a smooth aluminum plate. 12 g of a composition (aqueous dispersion) containing polymer particles adjusted to a solid content of 5% was poured there. After drying this at room temperature for 24 hours, a 200-micrometer-thick film was obtained by drying at 100 degreeC for 1 hour. Using a micro durometer, the probe was pressed against the film at a load of 30 mN/20 s, and then held for 5 s. In addition, the indentation depth was evaluated by increasing the load and unloading under the same conditions. The elastic deformation rate was calculated from the obtained load-displacement curve.

(glass transition temperature)

The composition containing polymer particles was adjusted to pH 7.0 and dried at 130°C for 30 minutes to obtain a dried product. Using differential scanning calorimetry (manufactured by SII Nanotechnology Co., Ltd.; DSC6220), the temperature was raised from -50°C to +200°C at a rate of 20°C/min according to the ASTM method (D3418-97), and the polymer particles A differential scanning calorimetry curve was obtained, and the glass transition temperature was determined using the attached software. Whether or not there was one glass transition temperature or two or more was determined by obtaining a peak according to software judgment.

In addition, the glass transition temperature of the core portion was measured in the same manner as above except that a polymer corresponding to the core portion obtained by the method described in the section (Young's modulus) was used.

In addition, the glass transition temperature of the cell portion was measured in the same manner as above, except that a polymer corresponding to the cell portion obtained by the method described in the above (electrolyte solution swelling degree) was used.

(Peel Strength)

A test piece having a width of 2 cm and a length of 12 cm was cut out from the obtained secondary battery negative electrode, and the surface of the side surface of the current collector of this test piece was affixed to an aluminum plate with double-sided tape. In accordance with JIS Z 1522, a tape having a width of 18 mm (trade name "Cellotape (registered trademark)" (manufactured by Nichiban Co.)) was attached to the electrode layer side of the test piece, and the tape was applied at a rate of 100 mm/min in a 180° direction. The strength at the time of peeling was measured 6 times, and the average value (N/18 mm) was calculated as the peel strength (before electrolyte solution immersion). Next, a test piece having a width of 2 cm and a length of 12 cm was separately cut out from the secondary battery negative electrode, and the test piece was immersed in a mixed solvent of ethylene carbonate/ethylmethyl carbonate = 1/2 (volume ratio) at 80°C for 1 week. After that, using a test piece dried at 80°C for one day, the peel strength (after immersion in electrolyte solution) was measured in the same manner as above. The higher these values are, the higher the adhesive strength between the current collector and the electrode layer is, and it can be evaluated that the electrode layer is less easily peeled off from the current collector. Specifically, the peel strength was evaluated based on the following criteria.

◎: 40 N/m or more

○: 30 N/m or more and less than 40 N/m

△: 20 N/m or more and less than 30 N/m

×: less than 20 N/m

(spring bag)

The thickness of the secondary battery negative electrode (negative electrode active material bulk density: 1.35 g/cm 3 ) immediately obtained by the method described in the section (Manufacture of secondary battery negative electrode) and the thickness after being left for one day is measured, and the difference is calculated as springback. and evaluated based on the following criteria.

◎ : Less than 5 μm

○: 5 μm or more and less than 10 μm

△: 10 μm or more and less than 15 μm

×: 15 µm or more

(rebound)

From the thickness after pressing the obtained secondary battery negative electrode and leaving it to stand for one day, the thickness of the electrode layer after injecting an electrolyte described later and repeating charging and discharging for 100 cycles was measured.

Rebound property = (thickness of electrode layer after 100 cycles of charging and discharging) - (thickness after being pressed and left for 1 day)

Evaluation was made based on the following criteria.

◎: Less than 10 μm

○: 10 μm or more and less than 15 μm

△: 15 μm or more and less than 20 μm

×: 20 µm or more

(initial capacity, temperature cycle test and cycle characteristics)

Using a secondary battery negative electrode, the secondary battery produced by the following method was charged with a constant current until it reached 4.2 V by a constant current constant voltage charging method at 2 C at 60 ° C., and then charged at a constant voltage, Subsequently, a charge/discharge cycle of discharging to 3.0 V at a constant current of 2 C was performed. The cycle test was carried out up to 100 cycles, and the ratio of the discharge capacity at the 100th cycle to the initial discharge capacity was determined as the capacity retention rate, based on the following criteria. The larger this value is, the smaller the sense of capacity by repeated charging and discharging is.

◎: Capacity retention rate is 90% or more

○: capacity retention rate of 80% or more and less than 90%

△: capacity retention rate of 70% or more and less than 80%

×: Capacity retention rate is less than 70%

<Manufacture of secondary battery>

The secondary battery positive electrode and negative electrode were punched out in a circular shape, and the positive electrode, separator, and negative electrode were stacked in this order so that the active material surfaces of the positive electrode and negative electrode faced each other, and then stored in a stainless steel container with a cover. The container and the cover are insulated, and the container is placed in contact with the copper foil of the negative electrode and the cover is in contact with the aluminum foil of the positive electrode, respectively. Then, the electrolyte solution was poured into the container, sealed, and allowed to stand at room temperature for one day in that state to manufacture a secondary battery.

The electrolyte used here was prepared by dissolving LiPF ₆ as a solute in a mixed solvent of ethylene carbonate/ethylmethyl carbonate = 1/2 (volume ratio) to a concentration of 1.0 mol/L.

In addition, a polyethylene porous film was used for the separator, and the secondary battery negative electrode obtained in Examples 1 to 10 and Comparative Examples 1 to 5 was used for the secondary battery negative electrode.

In addition, what was manufactured as follows was used for the said secondary battery positive electrode.

92.2 mass% of lithium cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 2.3 mass% each of flaky graphite and acetylene black as a conductive material, and 3.2 mass% of polyvinylidene fluoride (PVDF) as a binder, N-methylpyrrolidone ( NMP) to prepare a slurry. This slurry was applied with a die coater to one side of an aluminum foil having a thickness of 20 μm to serve as a positive electrode current collector, dried at 130° C. for 3 minutes, and then compression molded with a roll press. At this time, the active material coating amount of the positive electrode was 250 g/m 2 and the active material bulk density was 3.00 g/cm 3 . The electrode thus obtained was used as a secondary battery positive electrode.

Claims (10)

A polymer composition for a non-aqueous secondary battery electrode containing polymer particles,
The Young's modulus of the polymer particles is 1.5 GPa or less,
The elastic deformation rate of the polymer particles is 50% or less,
The polymer composition for non-aqueous secondary battery electrodes, wherein the swelling degree of the polymer particles is 1.5 times or less in the electrolyte solution. According to claim 1,
The polymer particle has a core cell structure composed of a core portion and a cell portion,
The polymer composition for non-aqueous secondary battery electrodes, wherein the core portion has a Young's modulus of 0.1 GPa or less. According to claim 2,
The polymer composition for a non-aqueous secondary battery electrode, wherein the swelling degree of the cell part is 1.10 times or less. According to claim 2,
When the total ethylenic monomers constituting the core cell structure is 100 mass%, the core portion contains ethylenically unsaturated carboxylic acid esters of 40 mass% or more and 80 mass% or less, and the cell portion is 15 mass% or more 60 Containing an ethylenically unsaturated carboxylic acid or an alkali metal salt thereof at 0 mass% or less and an ethylenically unsaturated monomer containing an N atom of 0 mass% or more and 45 mass% or less,
A polymer composition for a non-aqueous secondary battery electrode containing 0.1 part by mass or less of an alkylene oxide structure and 0.3 part by mass or less of a sulfonic acid or a salt thereof, based on 100 parts by mass of all ethylenic monomers constituting the core cell structure. . According to claim 2,
A polymer composition for non-aqueous secondary battery electrodes containing an N atom-containing ethylenically unsaturated monomer whose cell portion is 15 mass% or more and 30 mass% or less when all ethylenic monomers constituting the core cell structure are 100 mass%. According to claim 1,
The polymer composition for non-aqueous secondary battery electrodes whose maximum glass transition temperature of the said polymer particle measured by DSC is 20 degreeC or less. According to claim 1,
The polymer composition for non-aqueous secondary battery electrodes whose average particle diameter of the said polymer particle is 50 nm or more and 800 nm or less. According to claim 2,
The polymer composition for non-aqueous secondary battery electrodes whose mass ratio of the core part in the said core cell structure is 0.4 or more and 0.8 or less. According to claim 1,
The polymer composition for non-aqueous secondary battery electrodes, which further contains an isothiazoline-based compound of 0.0001 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the polymer particles. A nonaqueous secondary battery containing the polymer composition for nonaqueous secondary battery electrodes according to any one of claims 1 to 9.