阅读说明：本技术 非水系二次电池粘接层用浆料组合物、非水系二次电池用粘接层、非水系二次电池用间隔件以及非水系二次电池 (Slurry composition for nonaqueous secondary battery adhesive layer, adhesive layer for nonaqueous secondary battery, separator for nonaqueous secondary battery, and nonaqueous secondary battery ) 是由 田中庆一朗 于 2019-07-12 设计创作，主要内容包括：本发明提供一种非水系二次电池粘接层用浆料组合物,其包含有机颗粒、磺基琥珀酸酯或其盐、分子量为1000以下的烃以及水。(The present invention provides a slurry composition for a non-aqueous secondary battery adhesive layer, which comprises organic particles, sulfosuccinate or a salt thereof, a hydrocarbon having a molecular weight of 1000 or less, and water.)

1. A slurry composition for a non-aqueous secondary battery adhesive layer contains organic particles, sulfosuccinic acid ester or salt thereof, hydrocarbon having a molecular weight of 1000 or less, and water.

2. The slurry composition for a nonaqueous secondary battery adhesive layer according to claim 1, wherein the hydrocarbon having a molecular weight of 1000 or less is a chain saturated hydrocarbon.

3. The slurry composition for a non-aqueous secondary battery adhesive layer according to claim 1 or 2, wherein a content ratio of the sulfosuccinate or a salt thereof is 0.5 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the organic particles.

4. The slurry composition for a non-aqueous secondary battery adhesive layer according to any one of claims 1 to 3, wherein a content ratio of the sulfosuccinate or a salt thereof is 500 parts by mass or more and 20000 parts by mass or less with respect to 100 parts by mass of the hydrocarbon having a molecular weight of 1000 or less.

5. The slurry composition for a non-aqueous secondary battery adhesive layer according to any one of claims 1 to 4, wherein a content ratio of the hydrocarbon having a molecular weight of 1000 or less is 0.01 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the organic particles.

6. A method for producing an adhesive layer for a nonaqueous secondary battery, comprising the steps of:

a step of applying the slurry composition for the adhesive layer of a nonaqueous secondary battery according to any one of claims 1 to 5 on a separator base material to form a coating film, and

and drying the coating film to obtain an adhesive layer.

7. An adhesive layer for a nonaqueous secondary battery, which is formed by using the slurry composition for an adhesive layer for a nonaqueous secondary battery according to any one of claims 1 to 5.

8. A separator for a nonaqueous secondary battery, comprising the adhesive layer for a nonaqueous secondary battery according to claim 7.

9. A nonaqueous secondary battery comprising the adhesive layer for a nonaqueous secondary battery according to claim 7.

Technical Field

The present invention relates to a slurry composition for an adhesive layer of a nonaqueous secondary battery, an adhesive layer for a nonaqueous secondary battery, a separator for a nonaqueous secondary battery, and a nonaqueous secondary battery.

Background

Nonaqueous secondary batteries (hereinafter, sometimes abbreviated as "secondary batteries") such as lithium ion secondary batteries have characteristics of being small in size, light in weight, high in energy density, and capable of being repeatedly charged and discharged, and are used in a wide range of applications. In general, a secondary battery includes battery members such as a positive electrode, a negative electrode, and a separator for separating the positive electrode from the negative electrode and preventing a short circuit between the positive electrode and the negative electrode.

In recent years, in order to improve battery characteristics of secondary batteries, etc., the compounding of the composition used for forming the above-described battery member has been studied. For example, patent document 1 proposes a binder composition for a lithium ion secondary battery, which contains a particulate polymer, a water-soluble polymer, a sulfosuccinate or a salt thereof, and water. The binder composition described in patent document 1 is characterized in that the content of the acid group-containing monomer unit in the water-soluble polymer is 20 to 70 wt%, and the content of the sulfosuccinate or a salt thereof is 0.01 to 10 parts by weight based on 100 parts by weight of the total of the particulate polymer and the water-soluble polymer. Further, the binder composition described in patent document 1 can provide a lithium ion secondary battery and the like having excellent cycle characteristics and low-temperature output characteristics.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-160651.

Disclosure of Invention

Problems to be solved by the invention

With respect to each component blended in the conventional binder composition described in patent document 1, the cycle characteristics and low-temperature output characteristics of the secondary battery are improved from the following viewpoints. First, the particulate polymer can form point bonding between adherends, contributing to improvement in the output characteristics of the secondary battery obtained. The water-soluble polymer having a predetermined composition contributes to improvement in cycle characteristics of the obtained secondary battery by reducing precipitation of lithium ions in the electrolyte solution. Further, a prescribed amount of sulfosuccinic acid improves the coating property of the binder composition to contribute to improvement of the output characteristics and cycle characteristics of the resulting secondary battery.

However, in recent years, secondary batteries are required to have further higher output. Therefore, the separator of the secondary battery is required to have a property of being less likely to cause electrical breakdown when a high voltage is applied, that is, to have excellent voltage resistance.

However, when the conventional adhesive composition is used for forming a spacer, there is still room for further improvement in the voltage resistance of the obtained spacer.

Accordingly, an object of the present invention is to provide a slurry composition for an adhesive layer of a nonaqueous secondary battery, which can provide a separator having excellent voltage resistance when applied to a separator base material to form an adhesive layer.

Another object of the present invention is to provide an adhesive layer for a nonaqueous secondary battery, which can improve the voltage resistance of a separator.

Further, another object of the present invention is to provide a separator for a nonaqueous secondary battery and a nonaqueous secondary battery having excellent voltage resistance.

Means for solving the problems

The present inventors have conducted intensive studies in order to solve the above problems. Then, the present inventors newly found that when organic particles, sulfosuccinic acid and salts thereof, and low-molecular-weight hydrocarbons are added to prepare a slurry composition, the voltage resistance of the obtained spacer can be significantly improved, and completed the present invention.

That is, the present invention has been made to solve the above problems advantageously, and a slurry composition for a non-aqueous secondary battery adhesive layer according to the present invention is characterized by containing organic particles, sulfosuccinate or a salt thereof, a hydrocarbon having a molecular weight of 1000 or less, and water. According to the slurry composition having such a composition, a spacer having excellent withstand voltage can be provided when the slurry composition is applied to a spacer base material to form an adhesive layer.

The molecular weight of the hydrocarbon means a number average molecular weight, and can be measured by the measurement method described in examples.

In the slurry composition for a nonaqueous secondary battery adhesive layer of the present invention, the hydrocarbon having a molecular weight of 1000 or less is preferably a chain saturated hydrocarbon. According to the slurry composition containing the chain saturated hydrocarbon as the hydrocarbon having the molecular weight of 1000 or less, the spacer further excellent in the voltage resistance can be provided.

In the slurry composition for a non-aqueous secondary battery adhesive layer of the present invention, the content of the sulfosuccinate or a salt thereof is preferably 0.5 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the organic particles. If the content ratio of the sulfosuccinate or the salt thereof in the slurry composition is within the above range with respect to 100 parts by mass of the organic particles, a separator having further excellent voltage resistance can be provided, and a secondary battery having excellent cycle characteristics can be provided.

In the slurry composition for a non-aqueous secondary battery adhesive layer of the present invention, the content ratio of the sulfosuccinate or a salt thereof is preferably 500 parts by mass or more and 20000 parts by mass or less with respect to 100 parts by mass of the hydrocarbon having a molecular weight of 1000 or less. If the content ratio of the sulfosuccinate or the salt thereof in the slurry composition is within the above range with respect to 100 parts by mass of the hydrocarbon having a molecular weight of 1000 or less, a separator having further excellent voltage resistance and process adhesion properties can be provided, and a secondary battery having further excellent cycle characteristics can be provided.

In the slurry composition for a non-aqueous secondary battery adhesive layer of the present invention, the content ratio of the hydrocarbon having a molecular weight of 1000 or less is preferably 0.01 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the organic particles. In this manner, if the content ratio of the hydrocarbon having a molecular weight of 1000 or less in the slurry composition is within the above range with respect to 100 parts by mass of the organic particles, a spacer having further excellent voltage resistance and process adhesiveness can be provided.

In addition, in order to advantageously solve the above problems, the present invention provides a method for producing an adhesive layer for a nonaqueous secondary battery, comprising a step of applying any one of the slurry compositions for an adhesive layer for a nonaqueous secondary battery to a separator base material to form a coating film and a step of drying the coating film to obtain an adhesive layer. According to the production method of the present invention including the step of applying any one of the slurry compositions for a nonaqueous secondary battery adhesive layer described above to a separator base material to form a coating film, it is possible to efficiently provide a nonaqueous secondary battery adhesive layer capable of improving the voltage resistance of the separator.

Further, in order to advantageously solve the above-mentioned problems, the adhesive layer for a nonaqueous secondary battery according to the present invention is formed by using any one of the slurry compositions for an adhesive layer for a nonaqueous secondary battery. Such an adhesive layer for a nonaqueous secondary battery according to the present invention can improve the voltage resistance of the separator.

Further, in order to advantageously solve the above-described problems, the present invention provides a separator for a nonaqueous secondary battery, which comprises the adhesive layer for a nonaqueous secondary battery of the present invention. The nonaqueous secondary battery separator of the present invention has excellent voltage resistance.

In addition, in order to advantageously solve the above-described problems, the nonaqueous secondary battery of the present invention is characterized by having the adhesive layer for a nonaqueous secondary battery. Such a nonaqueous secondary battery of the present invention has excellent voltage resistance.

Effects of the invention

According to the present invention, it is possible to provide a slurry composition for an adhesive layer of a nonaqueous secondary battery, which can provide a separator having excellent voltage resistance when applied to a separator base material to form an adhesive layer.

Further, according to the present invention, it is possible to provide an adhesive layer for a nonaqueous secondary battery, which can improve the voltage resistance of a separator.

Further, according to the present invention, it is possible to provide a separator for a nonaqueous secondary battery and a nonaqueous secondary battery having excellent voltage resistance.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

The slurry composition for a nonaqueous secondary battery adhesive layer of the present invention can be used for forming the adhesive layer for a nonaqueous secondary battery of the present invention. The adhesive layer for a nonaqueous secondary battery of the present invention constitutes a spacer together with a spacer base material, and bonds the spacer to other battery members such as an electrode. The separator for a nonaqueous secondary battery and the nonaqueous secondary battery of the present invention are characterized by having the adhesive layer for a nonaqueous secondary battery of the present invention.

(slurry composition for nonaqueous Secondary Battery adhesive layer)

The slurry composition for a nonaqueous secondary battery adhesive layer of the present invention (hereinafter, also simply referred to as "the slurry composition of the present invention") is characterized by containing organic particles, sulfosuccinate or a salt thereof, a hydrocarbon having a molecular weight of 1000 or less, and water. Further, the slurry composition of the present invention may optionally contain a binder, a leveling agent, and other additives.

Here, the reason why a spacer having excellent voltage resistance can be provided when the slurry composition of the present invention satisfying the above-described composition is applied to a spacer base material to form an adhesive layer is not clearly understood, but the reason is presumed to be as follows.

That is, the sulfosuccinate or a salt thereof contained in the slurry composition of the present invention functions to appropriately promote the entry of hydrocarbons having a molecular weight of 1000 or less into pores of the microporous membrane when the slurry composition is applied to a spacer substrate formed of the microporous membrane in forming an adhesive layer. It is also presumed that if the hydrocarbon enters the pores of the microporous membrane to an appropriate degree, the insulation of the entire separator can be improved.

< organic particles >

The organic particles are particles made of a polymer that exhibit adhesive ability, anti-blocking performance, and the like in the adhesive layer. The organic particles can be stably present in the slurry composition for an adhesive layer and in the electrolyte solution of a secondary battery while maintaining the particle shape. In addition, the organic particles can be used alone in 1, also can be combined with more than 2.

< Structure of organic particle >)

The structure of the organic particles is not particularly limited, and the organic particles may be particles containing a non-composite polymer composed of substantially a single polymer component, or may be particles containing a composite polymer composed of a plurality of polymer components.

Examples of the particles containing a non-composite polymer include polyethylene particles, polystyrene particles, polydivinylbenzene particles, styrene-divinylbenzene copolymer crosslinked material particles, polyimide particles, polyamide particles, polyamideimide particles, melamine resin particles, phenol resin particles, benzoguanamine-formaldehyde condensate particles, polysulfone particles, polyacrylonitrile particles, polyaramide particles, polyacetal particles, polymethyl methacrylate particles, and the like.

The particle containing the composite polymer is a heterogeneous structure in which polymer portions different from each other exist inside the particle. Here, the heterogeneous structure refers to a single particle formed by physically or chemically bonding 2 or more different polymers, and is not a particle having a single phase structure formed of a single polymer such as a block polymer. Specific examples of the heterogeneous structure include: a core-shell structure having a core portion and a shell portion covering at least a part of an outer surface of the core portion; a side-by-side structure in which 2 or more polymers are arranged in parallel; a snowman structure in which a part of the polymer in the center portion is exposed to the outer shell portion in the core-shell structure; an octopus structure, which is a structure in which spherical polymer particles are integrated by embedding other types of polymer particles into the surfaces thereof.

Among these, the organic particles are preferably a polymer having a core-shell structure (hereinafter, may be abbreviated as "core-shell polymer") from the viewpoint of improving the blocking resistance of the adhesive layer. In addition, "blocking resistance" means the following properties: in the storage and transportation of the battery member (i.e., the spacer) having the adhesive layer, the property that the battery members adjacent via the adhesive layer adhere to each other (i.e., stick) can be suppressed. Whether or not the organic particles have a core-shell structure can be confirmed by observation of the cross-sectional structure of the organic particles.

[ organic particles as core-Shell Polymer ]

The organic particles as the core-shell polymer have a core portion and a shell portion covering an outer surface of the core portion. Here, the shell portion preferably partially covers an outer surface of the core portion. That is, the shell portion of the organic particle as the core-shell polymer preferably covers the outer surface of the core portion but does not cover the entire outer surface of the core portion. Even in a case where it appears in appearance that the outer surface of the core portion is completely covered by the shell portion, if a hole communicating the inside and the outside of the shell portion is formed, the shell portion is a shell portion that partially covers the outer surface of the core portion.

Nuclear part-

The polymer constituting the core portion (hereinafter, sometimes referred to as "core portion polymer") is not particularly limited, and a polymer obtained by polymerizing an arbitrary monomer can be used. Examples of monomers that can be used to prepare the polymer of the core portion include: vinyl chloride monomers such as vinyl chloride and vinylidene chloride; vinyl acetate monomers such as vinyl acetate; aromatic vinyl monomers such as styrene, α -methylstyrene, styrenesulfonic acid, butoxystyrene, and vinylnaphthalene; vinylamine-based monomers such as vinylamine; vinyl amide monomers such as N-vinylformamide and N-vinylacetamide; acid group-containing monomers such as a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, a monomer having a phosphoric acid group, and a monomer having a hydroxyl group; (meth) acrylic acid derivatives such as 2-hydroxyethyl methacrylate; (meth) acrylate monomers such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl acrylate, and 2-ethylhexyl acrylate; (meth) acrylamide monomers such as acrylamide and methacrylamide; (meth) acrylonitrile monomers such as acrylonitrile and methacrylonitrile; fluorine-containing (meth) acrylate monomers such as 2- (perfluorohexyl) ethyl methacrylate and 2- (perfluorobutyl) ethyl acrylate; a maleimide monomer; maleimide derivatives such as phenylmaleimide; diene monomers such as 1, 3-butadiene and isoprene. These may be used alone in 1 kind, or may be used in combination in 2 or more kinds at an arbitrary ratio.

In the present invention, "(meth) acrylic acid" means acrylic acid and/or methacrylic acid, "(meth) acryloyl" means acryloyl and/or methacryloyl, "(meth) acrylate" means acrylate and/or methacrylate

Among the above monomers, as a monomer that can be used for producing the polymer of the core portion, it is preferable to use at least any one of an aromatic vinyl monomer, an acid group-containing monomer, (meth) acrylate monomer, and a (meth) acrylonitrile monomer. That is, the polymer in the core portion preferably contains at least any one of an aromatic vinyl monomer unit, an acid group-containing monomer unit, a (meth) acrylate monomer unit, and a (meth) acrylonitrile monomer unit, and more preferably contains at least a (meth) acrylate monomer unit and an acid group-containing monomer unit. In the above, styrene units are preferred as the aromatic vinyl monomer units, methyl methacrylate units and n-butyl acrylate units are preferred as the (meth) acrylate monomer units, acrylonitrile units are preferred as the (meth) acrylonitrile monomer units, and acrylic acid units are preferred as the acid group-containing monomer units.

Further, the polymer of the core portion may contain a crosslinkable monomer unit. Examples of the crosslinkable monomer unit include units derived from a polyfunctional monomer such as allyl methacrylate.

In the present invention, "containing a monomer unit" means "containing a repeating unit derived from the monomer in a polymer obtained using the monomer".

When the total of the repeating units contained in the polymer forming the core portion is defined as 100% by mass, the content ratio of each unit in the core portion is preferably in the following range.

The content ratio of the (meth) acrylate monomer unit in the core portion is preferably 50% by mass or more and 99% by mass or less.

The content ratio of the acid group-containing monomer unit in the core portion is preferably 0.1 mass% or more and 5 mass% or less.

The content ratio of the crosslinkable monomer unit in the core portion is preferably 0.1% by mass or more and 5% by mass or less.

-shell-

The polymer constituting the shell portion (hereinafter, sometimes referred to as "shell portion polymer") is not particularly limited, and a polymer obtained by polymerizing an arbitrary monomer can be used. Specifically, examples of monomers that can be used for preparing the polymer of the shell portion include the same monomers as exemplified as monomers that can be used for producing the polymer of the core portion. Further, such monomers may be used alone in 1 kind, or may be used in combination in 2 or more kinds at an arbitrary ratio. Among them, the polymer of the shell portion preferably contains an aromatic vinyl monomer unit and an acid group-containing monomer unit.

When all the repeating units contained in the polymer forming the shell portion are assumed to be 100% by mass, the content ratio of the aromatic vinyl monomer unit in the shell portion is preferably 50% by mass or more and less than 100% by mass. Further, the proportion of the acid group-containing monomer unit in the shell portion is preferably 0.1 mass% or more and 7 mass% or less.

< method for producing organic particles >)

The method for producing the organic particles is not particularly limited. For example, any of solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, and the like can be used as a polymerization method for producing organic particles as non-composite polymers. Further, as the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, living radical polymerization, and the like can be used. Further, as the emulsifier, dispersant, polymerization initiator, chain transfer agent and the like which can be used for polymerization, commonly used emulsifiers, dispersants, polymerization initiators, chain transfer agents and the like can be used, and the amount thereof can be used in a commonly used amount.

Furthermore, the organic particles, for example as core-shell polymers, can be prepared by the following method: the polymerization is performed in stages by using monomers of the polymer of the core portion and monomers of the polymer of the shell portion, and changing the ratio of these monomers with time. Specifically, the organic particles as the core-shell polymer can be produced by a continuous multistage emulsion polymerization method and a multistage suspension polymerization method in which a polymer in a subsequent stage sequentially coats a polymer in a previous stage.

Examples of the case where the organic particles as the core-shell polymer are obtained by multistage emulsion polymerization include the method described in international publication No. 2016/110894.

< Properties of organic particles >

When the organic particles are non-composite polymers, the glass transition temperature of the organic particles is preferably 50 ℃ or higher and 100 ℃ or lower. If the glass transition temperature of the organic particles is not less than the lower limit, the blocking resistance of the obtained spacer can be further improved. Further, if the glass transition temperature of the organic particles is not higher than the upper limit, the adhesiveness as an adhesive layer can be sufficiently improved.

When the organic particles have a core-shell structure, the glass transition temperature of the core portion is preferably 35 ℃ or higher and 70 ℃ or lower, and the glass transition temperature of the shell portion is preferably 80 ℃ or higher and 150 ℃ or lower. By satisfying these conditions, the technical effect of sufficiently improving the adhesiveness as an adhesive layer and the technical effect of improving the blocking resistance of the obtained spacer can be achieved at the same time at a high level.

In addition, the glass transition temperature of the organic particles can be adjusted to a desired value based on the composition at the time of production. The glass transition temperature of the organic particles can be measured by the method described in the examples.

The organic particles preferably have an electrolyte swelling degree of 100% or more and 1000% or less, more preferably 100% or more and 800% or less, and still more preferably 200% or more and 550% or less. If the electrolyte swelling degree of the organic particles is within the above range, the rate characteristics of the obtained secondary battery can be further improved. In addition, the electrolyte swelling degree of the organic particles can be adjusted to a desired value based on the composition at the time of production. The degree of swelling in the electrolyte of the organic particles can be measured by the method described in examples.

< sulfosuccinic acid ester or salt thereof >

The sulfosuccinic acid ester is a monoester, diester or triester of sulfosuccinic acid, preferably a monoester or diester, and more preferably a diester. The sulfosuccinate is preferably a monoalkyl ester, a dialkyl ester or a trialkyl ester, more preferably a monoalkyl ester or a dialkyl ester, and still more preferably a dialkyl ester.

More specifically, the sulfosuccinate or a salt thereof is preferably a compound represented by the following formula (i).

[ chemical formula 1]

In the formula (i), R¹And R²Each independently selected from Na, K, Li, NH₄And an alkyl group having 1 to 12 carbon atoms, X is selected from Na, K, Li and NH₄. At R¹And R²When each alkyl group is used, the number of carbon atoms is more preferably 1 to 12, still more preferably 2 to 10. At R¹And R²When each alkyl group is a straight-chain alkyl group, a branched alkyl group, or an alkyl group having an alicyclic structure may be used. Preferable examples of such an alkyl group include octyl, cyclohexyl, cyclopentyl and pentyl. Among these, octyl, cyclohexyl, cyclopentyl and pentyl groups are particularly preferable, and octyl is most preferable.

In formula (i), X is preferably selected from Na, Li and NH₄More preferably selected from Na and Li. In addition, in R¹And R²In the case where each is a group other than an alkyl group, they are also preferably selected from Na and Li. At R¹And R²In the case where each is a group other than an alkyl group, they are usually the same as X.

More specific examples of the compound represented by the formula (i) include sodium salts, potassium salts and ammonium salts of dioctyl sulfosuccinate, diamyl sulfosuccinate and dicyclopentyl sulfosuccinate.

In the slurry composition of the present invention, the content ratio of the sulfosuccinate or a salt thereof is preferably 0.5 parts by mass or more, more preferably 3.0 parts by mass or more, further preferably 5.0 parts by mass or more, particularly preferably 7.0 parts by mass or more, preferably 18 parts by mass or less, more preferably 13 parts by mass or less, further preferably 12 parts by mass or less, relative to 100 parts by mass of the organic particles. In the case where the slurry composition of the present invention contains both the sulfosuccinate and the salt thereof, the content ratio is the ratio of the total of the sulfosuccinate and the salt thereof to the organic particles. If the content ratio of the sulfosuccinate or a salt thereof is not less than the lower limit value with respect to the organic particles, the voltage resistance of the obtained separator can be further improved. Further, if the content ratio of the sulfosuccinate or a salt thereof is not higher than the above upper limit with respect to the organic particles, the cycle characteristics of the obtained secondary battery can be improved. It is inferred that this is because: when the content ratio of the sulfosuccinate or the salt thereof is not more than the upper limit, pores of the spacer base material are not clogged with the hydrocarbon having a molecular weight of 1000 or less.

In the slurry composition of the present invention, the content ratio of the sulfosuccinate or a salt thereof is preferably 5000 parts by mass or more, more preferably 7000 parts by mass or more, preferably 20000 parts by mass or less, and more preferably 14000 parts by mass or less, relative to 100 parts by mass of a hydrocarbon having a molecular weight of 1000 or less described later. If the content ratio of the sulfosuccinate or a salt thereof based on 100 parts by mass of the organic particles and the content ratio of the hydrocarbon having a molecular weight of 1000 or less satisfy the preferable ranges described above or below, and if the content ratio of the sulfosuccinate or a salt thereof based on 100 parts by mass of the hydrocarbon having a molecular weight of 1000 or less satisfies the preferable ranges described above, the following effects can be obtained. First, if the content ratio of the sulfosuccinate or a salt thereof is not less than the lower limit value with respect to the hydrocarbon having a molecular weight of 1000 or less, the voltage resistance of the resulting separator can be further improved. Further, if the content ratio of the sulfosuccinate or a salt thereof is not more than the above upper limit value with respect to the hydrocarbon having a molecular weight of 1000 or less, the process adhesiveness of the adhesive layer can be improved, and the cycle characteristics of the obtained secondary battery can be improved. The "technical adhesiveness" of the adhesive layer means adhesiveness in a state before immersion in the electrolyte. In other words, the term "adhesiveness" refers to the adhesiveness between battery members in a state before the electrolyte is injected in the manufacturing process of the secondary battery.

< hydrocarbons having a molecular weight of 1000 or less >

The hydrocarbon having a molecular weight of 1000 or less can enter the pores of the spacer base material to function to improve the voltage resistance of the spacer. Further, when the hydrocarbons having a molecular weight of 1000 or less are present in a state of being adsorbed or adhered to the surface of the organic particles, they exhibit a function of improving the process adhesiveness of the adhesive layer by exhibiting plasticization.

The molecular weight (number average molecular weight) of the hydrocarbon is required to be 1000 or less, preferably 550 or less, preferably 500 or less, preferably 70 or more, more preferably 200 or more, and further preferably 250 or more. If the molecular weight of the hydrocarbon is within the above range, the technical effect of improving the process adhesiveness of the obtained adhesive layer and the technical effect of improving the voltage resistance of the obtained spacer can be achieved at the same time. More specifically, the hydrocarbon having a molecular weight within the above range can function as a plasticizer in the adhesive layer to improve the process adhesiveness of the adhesive layer. In particular, when the molecular weight of the hydrocarbon is not less than the lower limit, the effect of improving the voltage resistance of the spacer can be further improved by the hydrocarbon entering the pores of the spacer base material. In addition, when the molecular weight of the hydrocarbon is not more than the above upper limit, the penetration of the hydrocarbon into the pores can be promoted when the slurry composition is applied to the spacer base material, and the voltage resistance of the obtained spacer can be improved.

The hydrocarbon is not particularly limited as long as the molecular weight satisfies the above range, and all hydrocarbons can be used. Therefore, the hydrocarbon having a molecular weight of 1000 or less may be any of an aliphatic hydrocarbon and an aromatic hydrocarbon having a molecular weight of 1000 or less. Among them, the hydrocarbons having a molecular weight of 1000 or less are preferably chain-type (straight-chain or branched-chain) saturated hydrocarbons having a molecular weight of 1000 or less. Specifically, examples of the chain saturated hydrocarbon having a molecular weight of 1000 or less include octane, nonane, decane and the like, and commercially available products thereof include MORESCO Corporation, MORESCO (registered trademark) WHITE series and the like.

The content of the hydrocarbon having a molecular weight of 1000 or less in the slurry composition is preferably 0.01 part by mass or more, more preferably 0.03 part by mass or more, further preferably 0.05 part by mass or more, preferably 1 part by mass or less, more preferably 0.5 part by mass or less, further preferably 0.2 part by mass or less, relative to 100 parts by mass of the organic particles. If the content ratio of the hydrocarbon having a molecular weight of 1000 or less is not less than the lower limit value with respect to 100 parts by mass of the organic particles, the process adhesiveness of the adhesive layer can be improved, and the voltage resistance of the obtained spacer can be further improved. Further, if the content ratio of the hydrocarbon having a molecular weight of 1000 or less is not more than the above upper limit value with respect to 100 parts by mass of the organic particles, the process adhesiveness of the adhesive layer can be improved.

< adhesive Material >

The binder is a component containing a polymer, and the binder plays a role of firmly bonding the battery members of the secondary battery, for example, the separator and the electrode, in the adhesive layer and prevents the above-mentioned component in the adhesive layer such as the organic particles from being detached from the adhesive layer.

< glass transition temperature of adhesive Material >)

Here, from the viewpoint of improving the adhesiveness of the adhesive layer, the glass transition temperature of the polymer constituting the adhesive (hereinafter, sometimes referred to as "glass transition temperature of the adhesive") is preferably less than 50 ℃, more preferably 25 ℃ or less, and still more preferably 15 ℃ or less. The lower limit of the glass transition temperature of the binder is not particularly limited, and may be, for example, -50 ℃ or higher. The glass transition temperature of the binder can be adjusted by changing the kind of monomer used for preparing the polymer constituting the binder, and the like.

The "glass transition temperature of the binder" can be measured by the method described in the examples.

< types of adhesive materials >)

The binder is not particularly limited as long as it is a polymer having binding ability, and any polymer can be used, and a particulate polymer dispersible in an aqueous medium can be preferably used. Specifically, examples of the binder include: diene polymers such as styrene-butadiene copolymers and acrylonitrile-butadiene copolymers; an acrylic polymer; a fluoropolymer; silicon polymers, and the like. Also, among these, acrylic polymers are preferable. These particulate polymers may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

[ acrylic acid Polymer ]

An acrylic polymer refers to a polymer comprising (meth) acrylate monomer units. The acrylic polymer preferably contains, for example, an acid group-containing monomer unit, an aromatic vinyl monomer unit, and a crosslinkable monomer unit in addition to the (meth) acrylate monomer unit. The acrylic polymer may contain a monomer unit (other monomer unit) other than the (meth) acrylate monomer unit, the aromatic vinyl monomer unit, and the crosslinkable monomer unit.

- (meth) propenyl ester monomer unit

As the (meth) acrylate ester monomer which can form the (meth) acrylate ester monomer unit of the acrylic polymer, those described in the item of "organic particles" can be cited. These may be used alone in 1 kind, or may be used in combination in an arbitrary ratio in 2 or more kinds. Also, among these, 2-ethylhexyl acrylate is preferable.

The proportion of the (meth) acrylate monomer unit in the acrylic polymer is preferably 40% by mass or more and 80% by mass or less.

Acid group-containing monomer units

As the acid group-containing monomer having an acid group-containing monomer unit which can form an acrylic polymer, those described in the section of "organic particles" can be cited. These may be used alone in 1 kind, or may be used in combination in an arbitrary ratio in 2 or more kinds. Also, among these, monomers having a carboxylic acid group are preferable, and acrylic acid is more preferable.

The proportion of the acid group-containing monomer unit in the acrylic polymer is preferably 1 mass% or more and 10 mass% or less.

Aromatic vinyl monomer units

As the aromatic vinyl monomer which can form the aromatic vinyl monomer unit of the acrylic polymer, there can be mentioned those described in the section of "organic particles". These may be used alone in 1 kind, or may be used in combination in an arbitrary ratio in 2 or more kinds. Of these, styrene is preferable.

The proportion of the aromatic vinyl monomer unit in the acrylic polymer is preferably 10% by mass or more and 50% by mass or less.

Crosslinkable monomer units

As the crosslinkable monomer which can form the crosslinkable monomer unit of the acrylic polymer, those described in the section of "organic particles" can be cited. These may be used alone in 1 kind, or may be used in combination in an arbitrary ratio in 2 or more kinds. Among these, allyl methacrylate is preferable.

The proportion of the crosslinkable monomer unit in the acrylic polymer is preferably 0.1 mass% or more and 6 mass% or less.

Other monomer units

The other monomer that can form another monomer unit is not particularly limited, and a monomer other than the (meth) acrylate monomer, the aromatic vinyl monomer, and the crosslinkable monomer among the monomers listed in the item of "organic particles" can be used. These may be used alone in 1 kind, or may be used in combination in an arbitrary ratio in 2 or more kinds.

< preparation method of adhesive Material >)

The method for producing the binder is not particularly limited. For example, any of solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, and the like can be used as a polymerization method in the production of the binder. Further, as the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, living radical polymerization, and the like can be used. Further, as the emulsifier, dispersant, polymerization initiator, chain transfer agent and the like which can be used for polymerization, commonly used emulsifiers, dispersants, polymerization initiators, chain transfer agents and the like can be used, and the amount thereof can be in a commonly used amount.

< content of Binder >

The content of the binder in the slurry composition is not particularly limited, and is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 15 parts by mass or more, preferably 30 parts by mass or less, more preferably 27 parts by mass or less, and further preferably 25 parts by mass or less, relative to 100 parts by mass of the organic particles. If the content of the binder is not less than the lower limit, the adhesiveness of the adhesive layer can be improved. On the other hand, if the content of the binder is not more than the above upper limit, the internal resistance of the obtained secondary battery can be reduced.

< leveling agent >

The leveling agent is an arbitrary component blended for smoothing the coating surface obtained when the slurry composition is coated on the spacer substrate. The leveling agent is not particularly limited, and a compound other than sulfosuccinate or a salt thereof, which can exhibit a surface-active action, can be used.

For example, a nonionic surfactant can be used as the leveling agent. As the nonionic surfactant, a polyethylene glycol type surfactant, a polyoxyalkylene alkyl ether type surfactant, a polyol type nonionic surfactant, a polyoxyethylene distyrenated phenyl ether, a polyoxyethylene tribenzylphenyl ether, a polyoxyalkylene alkyl ether, and the like can be used. These can be used singly or in combination of two or more. Among them, it is preferable to blend at least a polyethylene glycol type surfactant as the leveling agent. The content of the leveling agent in the slurry composition may be, for example, 0.05 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the organic particles.

< other additives >

As other additives that may be contained in the slurry composition of the present invention, known additives such as a viscosity modifier and an electrolyte additive may be mentioned. These are not particularly limited as long as they do not affect the battery reaction, and known additives can be used. These additives may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

< method for producing slurry composition >

The method for producing the slurry composition is not particularly limited, and the slurry composition is usually produced by mixing the organic particles, sulfosuccinate or a salt thereof, a hydrocarbon having a molecular weight of 1000 or less, and other optional components in an aqueous medium. The mixing method is not particularly limited, and mixing can be performed using a known mixing device. The aqueous medium may be used by mixing a hydrophilic solvent (e.g., alcohols) other than water with water as a main solvent in a range that can ensure the dissolved or dispersed state of each component. The content of water as the "main solvent" may be more than 50% by mass, preferably more than 80% by mass, and more preferably more than 90% by mass, assuming that all solvent components contained in the slurry composition are 100% by mass.

In addition, in the case where the organic particles are prepared as an aqueous dispersion, the water used for the preparation of the slurry composition may be water contained in the aqueous dispersion of the organic particles.

< surface tension of slurry composition >

The slurry composition preferably has a surface tension of 30mN/m or more, more preferably 33mN/m or more, preferably 45mN/m or less, and more preferably 37mN/m or less. If the surface tension of the slurry composition is not less than the lower limit, excessive penetration of hydrocarbons having a molecular weight of 1000 or less into the pores of the spacer base material can be suppressed, and the cycle characteristics of the obtained secondary battery can be further improved. Further, if the surface tension of the slurry composition is not more than the above upper limit value, the entry of hydrocarbons having a molecular weight of 1000 or less into the pores of the spacer base material can be appropriately promoted, and the voltage resistance of the obtained spacer can be further improved.

The surface tension of the slurry composition can be controlled by adjusting the amount of sulfosuccinate or a salt thereof blended with the leveling agent, the binder, and the like.

(adhesive layer for nonaqueous Secondary Battery)

The adhesive layer for a nonaqueous secondary battery of the present invention can be formed using the slurry composition for an adhesive layer for a nonaqueous secondary battery. The adhesive layer for a nonaqueous secondary battery contains the organic particles, sulfosuccinate or a salt thereof, a hydrocarbon having a molecular weight of 1000 or less, and other optional components. The organic particles are present in the slurry composition in a particle shape, but in the adhesive layer formed using the slurry composition, the organic particles may be in a particle shape or may be in any other shape. The adhesive layer for a nonaqueous secondary battery of the present invention can be used for producing the nonaqueous secondary battery of the present invention. Specifically, the adhesive layer for a nonaqueous secondary battery of the present invention is applicable to a spacer base material, and is used for bonding the separator of the present invention, which is formed by forming an adhesive layer on a spacer base material, to other battery members such as an electrode. The adhesive layer for a nonaqueous secondary battery of the present invention contains the organic particles, sulfosuccinate or a salt thereof, and a hydrocarbon having a molecular weight of 1000 or less, and therefore has excellent voltage resistance.

In addition, when the polymer constituting the organic particles or the like contains a crosslinkable monomer unit, the polymer may be crosslinked at the time of drying of the slurry composition or at the time of heat treatment optionally performed after drying, or the like (that is, the adhesive layer may contain a crosslinked material such as organic particles).

< substrate >

Here, the spacer base material to which the slurry composition is applied is not particularly limited, and known spacer base materials such as organic spacer base materials and the like can be mentioned. The organic separator substrate is a porous member formed of an organic material, and examples of the organic separator substrate include a microporous film and a nonwoven fabric made of a polyolefin resin such as polyethylene and polypropylene, an aromatic polyamide resin, and the like. Among them, polyethylene and polypropylene are preferable as the organic material forming the spacer base material.

Further, the spacer base material preferably has a void ratio of 40% or more, more preferably 45% or more, further preferably 47% or more, preferably 60% or less, more preferably 55% or less, further preferably 53% or less. If the porosity of the spacer base material is within the above range, the voltage resistance can be effectively improved by the slurry composition of the present invention. The porosity of the spacer base material can be measured by the method described in the examples.

Further, the spacer base material preferably has a thickness of 5 μm or more, more preferably 6 μm or more, further preferably 7 μm or more, preferably 16 μm or less, more preferably 14 μm or less, further preferably 12 μm or less. If the thickness of the spacer base material is within the above range, the voltage resistance can be effectively improved by the slurry composition of the present invention.

The thickness of the adhesive layer is preferably 0.3 μm or more and 5 μm or less. If the thickness of the adhesive layer is 0.3 μm or more, the voltage resistance and adhesion of the spacer can be improved. Further, if the thickness of the adhesive layer is 5 μm or less, the battery characteristics (particularly, output characteristics) of the secondary battery can be improved.

< method for producing adhesive layer for nonaqueous Secondary Battery >

The adhesive layer for a nonaqueous secondary battery of the present invention can be produced, for example, by the following steps: a step (1) of applying the slurry composition for a nonaqueous secondary battery adhesive layer to a spacer base material to form a coating film; and a step (2) of drying the obtained coating film to obtain an adhesive layer. According to such a production method, the adhesive layer of the present invention having excellent withstand voltage can be efficiently produced.

In step (1), the slurry composition is applied to the spacer base material to form a coating film. In the step (1), the slurry composition is preferably applied directly to the spacer base material, and the method for applying the slurry composition to the spacer base material is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, an gravure method, an extrusion method, a brush coating method, and the like.

In the step (2), the coating film is dried to obtain an adhesive layer. The drying method is not particularly limited, and a known method can be used. Specifically, there may be mentioned: drying with warm air, hot air and low-humidity air; vacuum drying; drying by irradiation with infrared rays, electron beams, or the like. The drying conditions are not particularly limited, but the drying temperature is preferably 40 to 150 ℃ and the drying time is preferably 30 seconds to 30 minutes.

(nonaqueous Secondary Battery separator)

The separator for a nonaqueous secondary battery of the present invention (hereinafter, also simply referred to as "the separator of the present invention") includes a separator base material and the adhesive layer for a nonaqueous secondary battery of the present invention. The adhesive layer is preferably provided directly on the surface of the spacer base material without interposing another layer therebetween. As the spacer base material, the same base material as described in (the adhesive layer for a nonaqueous secondary battery) section can be used. The spacer of the present invention can be formed by applying the slurry composition of the present invention on a base material and drying the composition. The separator for a nonaqueous secondary battery of the present invention is formed by forming the adhesive layer of the present invention containing the organic particles, sulfosuccinate or salt thereof, and hydrocarbon having a molecular weight of 1000 or less on a separator base material, and therefore has excellent voltage resistance.

(nonaqueous Secondary Battery)

The nonaqueous secondary battery of the present invention is characterized by having the adhesive layer for a nonaqueous secondary battery. In particular, the nonaqueous secondary battery of the present invention is characterized in that battery members (i.e., the separator and the electrode of the present invention) are bonded to each other via the adhesive layer for a nonaqueous secondary battery of the present invention. The nonaqueous secondary battery of the present invention is excellent in voltage resistance.

Specifically, the nonaqueous secondary battery of the present invention includes, for example, a positive electrode, a negative electrode, a separator, and an electrolytic solution, and at least one surface of the separator is a surface including the adhesive layer for a nonaqueous secondary battery. In the nonaqueous secondary battery of the present invention, the positive electrode and the separator and/or the negative electrode and the separator are bonded and integrated via the adhesive layer for a nonaqueous secondary battery.

As the positive electrode, the negative electrode, the separator, and the electrolyte solution, known positive electrodes, negative electrodes, separators, and electrolyte solutions that can be used in nonaqueous secondary batteries can be used.

Specifically, as the electrodes (positive electrode and negative electrode), an electrode in which an electrode composite material layer is formed on a current collector can be used. As the current collector, a current collector made of a metal material such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum can be used. Among these, as the current collector for the negative electrode, a current collector made of copper is preferably used. As the current collector for the positive electrode, a current collector made of aluminum is preferably used. Further, as the electrode composite layer, a layer containing an electrode active material and a binder can be used.

In addition, as the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is generally used. For example, in the case where the nonaqueous secondary battery is a lithium ion secondary battery, a lithium salt may be used as the supporting electrolyte. Examples of the lithium salt include LiPF₆、LiAsF₆、LiBF₄、LiSbF₆、LiAlCl₄、LiClO₄、CF₃SO₃Li、C₄F₉SO₃Li、CF₃COOLi、(CF₃CO)₂NLi、(CF₃SO₂)₂NLi、(C₂F₅SO₂) NLi, etc. Among these, LiPF is preferable because it is easily soluble in a solvent and exhibits a high dissociation degree₆、LiClO₄、CF₃SO₃Li, particularly preferably LiPF₆. Further, 1 kind of electrolyte may be used alone, or 2 or more kinds may be used in combination at an arbitrary ratio. Since the lithium ion conductivity tends to be higher with a supporting electrolyte having a higher dissociation degree, the lithium ion conductivity can be adjusted by the kind of the supporting electrolyte.

Further, the organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte, and for example, in a lithium ion secondary battery, it is preferable to use: carbonates such as dimethyl carbonate (DMC), Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC), Butylene Carbonate (BC), Ethyl Methyl Carbonate (EMC), and Vinylene Carbonate (VC); esters such as γ -butyrolactone and methyl formate; ethers such as 1, 2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide, and the like. Further, a mixed solution of these solvents may also be used. Among them, carbonates are preferable because of high dielectric constant and wide stable potential region. Since the lithium ion conductivity generally tends to be higher as the viscosity of the solvent used is lower, the lithium ion conductivity can be adjusted by the kind of the solvent.

In addition, the concentration of the electrolyte in the electrolytic solution can be appropriately adjusted. In addition, known additives may be added to the electrolyte.

< method for producing nonaqueous Secondary Battery >

The nonaqueous secondary battery of the present invention can be produced, for example, by: the positive electrode and the negative electrode are stacked with a separator interposed therebetween, and the stack is wound, folded, or the like according to the battery shape as necessary, and placed in a battery container, and an electrolyte solution is injected into the battery container, followed by sealing. In order to prevent the pressure rise, overcharge, discharge, and the like in the nonaqueous secondary battery, an overcurrent prevention element such as a fuse or a PTC element, a porous metal mesh, a guide plate, and the like may be provided as necessary. The shape of the secondary battery may be any of coin type, button type, sheet type, cylindrical type, rectangular type, flat type, and the like, for example.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following description, "%" and "part" of the amounts are based on mass unless otherwise specified.

In addition, in a polymer produced by copolymerizing a plurality of monomers, unless otherwise specified, the proportion of a structural unit formed by polymerizing a certain monomer in the polymer is generally the same as the ratio (feed ratio) of the certain monomer in the total monomers used for polymerization of the polymer.

In the examples and comparative examples, the electrolyte swelling degree of organic particles, the glass transition temperature of each polymer, the molecular weight of hydrocarbon, the surface tension of the slurry composition, the porosity of the separator substrate, the voltage resistance of the separator, the process adhesiveness of the adhesive layer, and the cycle characteristics of the secondary battery were measured or evaluated in the following manner.

(degree of swelling of organic particles in electrolyte)

The aqueous dispersions containing organic particles prepared in examples and comparative examples were placed in a polytetrafluoroethylene petri dish and dried at 25 ℃ for 48 hours to produce a film having a thickness of 0.5 mm. The film was cut into 1cm square to obtain test pieces. The quality of the test piece was measuredIs W0. The test piece was immersed in the electrolyte solution at 60 ℃ for 72 hours. Then, the test piece was taken out of the electrolytic solution, and the electrolytic solution on the surface of the test piece was wiped to measure the mass W1 of the test piece after the immersion test. As the electrolyte, a mixed solvent of ethylene carbonate, diethyl carbonate and vinylene carbonate (volume mixing ratio ethylene carbonate/diethyl carbonate/vinylene carbonate is 68.5/30/1.5; SP value is 12.7 (cal/cm)³)^1/2) In which LiPF as a supporting electrolyte was dissolved at a concentration of 1mol/L₆The solution of (1).

The swelling degree S (%) was calculated as S ═ W1/W0 × 100 using their masses W0 and W1.

(glass transition temperature)

The glass transition temperatures of the organic particles and the binder material were measured according to their structures in the following manner.

< adhesive Material >

As the binder, an aqueous dispersion containing the binder was prepared, and the aqueous dispersion was dried and cured to obtain a measurement sample. 10mg of the measurement sample was weighed into an aluminum pan, and the measurement was carried out using a differential thermal analyzer ("EXSTAR DSC 6220" manufactured by SII Nanotechnology Inc.) under conditions specified in JIS Z8703 with a measurement temperature range of-100 ℃ to 500 ℃ and a temperature rise rate of 10 ℃/min, to obtain a Differential Scanning Calorimetry (DSC) curve. In addition, an empty aluminum pan was used as a control. The glass transition temperature (. degree. C.) was determined as the intersection of the base line of the DSC curve immediately before the onset of the endothermic peak and the tangent line of the DSC curve at the inflection point at which the first onset occurs after the endothermic peak, at which the differential signal (DDSC) became 0.05 mW/min/mg or more during the temperature rise.

< organic particles (core-Shell Polymer) >

First, as for the polymers of the core portion and the shell portion of the core-shell polymer as the organic particles, aqueous dispersions containing the polymers (the polymer of the core portion and the polymer of the shell portion) are prepared, respectively, using monomers, various additives, and the like used in the formation of the core portion and the shell portion, under the same polymerization conditions as those of the core portion and the shell portion. The aqueous dispersion thus prepared was dried and coagulated to obtain a measurement sample. Subsequently, the glass transition temperature (. degree. C.) of the polymer in the core portion and the glass transition temperature (. degree. C.) of the polymer in the shell portion were determined in the same manner as in the above non-composite polymer.

(molecular weight of Hydrocarbon)

Regarding the molecular weight distribution and the number average molecular weight (Mn) by Gel Permeation Chromatography (GPC) of the hydrocarbons used in examples and comparative examples, Tetrahydrofuran (THF) -soluble components of the samples were measured by GPC (gel permeation chromatography) using THF as a solvent. The measurement conditions are as follows.

(1) Preparation of measurement sample

The hydrocarbon (sample) was mixed with THF at a concentration of 5mg/ml, and after leaving at room temperature for 5 to 6 hours, shaking was sufficiently, the THF and the sample were mixed sufficiently until the agglomeration of the sample disappeared. Further, the mixture was allowed to stand at room temperature for 12 hours or more. In this case, the time from the time point when the sample and THF were mixed to the time point when the standing was completed was 24 hours or more.

Then, a sample passed through a sample treatment filter (pore size 0.45 to 0.5. mu.m, MysholdiscH-25-2 [ manufactured by TOSOH CORPORATION ]) was used as a sample for GPC.

(2) Measurement of samples

The column was stabilized in a hot chamber at 40 ℃ and THF as a solvent was passed through the column at this temperature at a flow rate of 1ml per minute, and 200. mu.l of a hydrocarbon THF sample solution adjusted to a sample concentration of 5mg/ml was injected and measured.

When the molecular weight of a sample is measured, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value and the measured number of a calibration curve prepared using a plurality of types of monodisperse polystyrene standard samples.

As a standard polystyrene sample for preparing a calibration curve, a polystyrene sample having a molecular weight of 6X 10, manufactured by Pressure chemical Co., Ltd., or manufactured by Toyo Cao Co., Ltd., was used²、2.1×10³、4×10³、1.75×10⁴、5.1×10⁴、1.1×10⁵、3.9×10⁵、8.6×10⁵、2×10⁶、4.48×10⁶The standard polystyrene sample of (4). In addition, the detector uses RI: (Refractive index) detector.

In addition, the columns are designed to be exactly aligned to 1 × 10³To 2X 10⁶The molecular weight region of (a) was measured, and a plurality of commercially available polystyrene gel columns were used in combination as described below. The measurement conditions of GPC are as follows.

[ GPC measurement conditions ]

The device comprises the following steps: LC-GPC 150C (made by Waters Corporation)

Column: KF801, 802, 803, 804, 805, 806, 807 (made by Shodex) 7-root tandem

Column temperature: 40 deg.C

Mobile phase: THF (tetrahydrofuran)

(surface tension)

The surface tension of the slurry compositions for a non-aqueous secondary battery adhesive layer produced in examples and comparative examples was measured by the platinum plate method using an automatic surface tension meter (DY-300, manufactured by synechia scientific co., ltd.).

(porosity of spacer base Material)

A10 cm × 10cm square sample was cut from the microporous membrane, and the volume (cm) thereof was determined³) And a mass (g) obtained from the volume and mass, and the density of polyethylene (0.95 g/cm)³) The calculation was performed using the following formula.

Void ratio (%) - (volume-mass/density of polyethylene)/volume × 100

(Voltage resistance)

The voltage resistance of the spacers produced in the examples and comparative examples was evaluated by the following procedure using a pulse tester model IMP-3090 manufactured by Nippon Technart inc. First, a spacer sample cut to 50mm × 50mm was sandwiched between electrodes (chromium iron plating) having a diameter of 30mm, and voltage application to the electrodes was started. The voltage value was increased by 0.05kV each time starting from 0.1 kV. The voltage is then continuously applied until a final electrical breakdown, i.e. a voltage drop, is detected. The voltage at the time when the voltage drop was detected was taken as the withstand voltage value. This test was performed on 10 spacer samples, and the average of the obtained withstand voltage values was used as a measured value. Then, the obtained measurement values were evaluated according to the following criteria to obtain an evaluation value of the withstand voltage of the spacer.

A (remarkably good): 1.7kV or more

B (good): 1.0kV or more and less than 1.7kV

C (optional): less than 1.0kV

(Process adhesion)

The positive electrode, the negative electrode and the separator prepared in examples and comparative examples were cut into a size of 10mm in width and 50mm in length, the positive electrode and the separator and the negative electrode and the separator were laminated, and the laminated body was pressed at 10 m/min by a roll press having a temperature of 80 ℃ and a load of 1MPa to prepare a test piece. In this test piece, the surface of the electrode (positive electrode or negative electrode) on the current collector side was faced downward, and a transparent tape was attached to the surface of the electrode. In this case, a transparent tape prescribed in JIS Z1522 was used. Further, the scotch tape was previously fixed on a horizontal test stand. Then, one end of the spacer base material was pulled vertically upward at a pulling rate of 50 mm/min, and the stress at that time was measured. The measurement was performed 3 times for each of the laminate having the positive electrode and the separator and the laminate having the negative electrode and the separator, and the total of the measurements was performed 6 times, and the average value of the stress was obtained as the peel strength, and the adhesiveness between the electrode and the separator was evaluated according to the following criteria. The higher the peel strength, the higher the technical adhesiveness (adhesiveness in a state of not being immersed in the electrolytic solution) of the adhesive layer.

A: peel strength of 5N/m or more

B: a peel strength of 3N/m or more and less than 5N/m

C: peel strength of less than 3N/m

(characteristics of cycle)

The following charge and discharge were repeated for 200 cycles for the fabricated lithium ion secondary battery: charging to 4.2V at constant current of 1.5C, charging to current of 0.02C at constant voltage, and discharging to 3.0V at 45 deg.C. Then, the charge/discharge capacity retention ratio represented by the ratio of the capacity at the end of 200 cycles to the capacity at the end of 5 cycles (capacity at the end of 200 cycles/capacity at the end of 5 cycles) × 100 (%)) was obtained. These measurements were performed on lithium ion secondary batteries of 5 battery cells, and the average value of the charge/discharge capacity retention rates of the respective battery cells was used as the charge/discharge capacity retention rate, and evaluated according to the following criteria. The larger this value, the more excellent the cycle characteristics.

A: the charge/discharge capacity retention ratio is 95% or more

B: the charge-discharge capacity retention rate is more than 90 percent and less than 95 percent

D: the charge-discharge capacity retention rate is less than 90 percent

(example 1)

< preparation of organic particles >

Adding the following components into a 5MPa pressure-resistant container with a stirrer: 53 parts of methyl methacrylate, 45 parts of butyl acrylate, 1 part of acrylic acid and 1 part of allyl methacrylate as a monomer composition for producing the core portion; 1 part of sodium dodecyl benzene sulfonate as an emulsifier; 150 parts of ion-exchanged water; and 0.5 part of potassium persulfate as a polymerization initiator, and sufficiently stirred. Then, the temperature was raised to 60 ℃ to initiate polymerization. The polymerization was continued until the polymerization conversion reached 96%, whereby an aqueous dispersion containing the polymer in the form of particles constituting the core portion was obtained.

Subsequently, the aqueous dispersion was heated to 70 ℃. 99 parts of styrene and 1 part of methacrylic acid as a monomer composition for producing the shell section were continuously supplied to the aqueous dispersion over 30 minutes, and polymerization was continued. The reaction was terminated by cooling when the polymerization conversion reached 96%, thereby producing an aqueous dispersion containing organic particles as the core-shell polymer. The organic particles produced in this step were confirmed to be core-shell structures in which the shell portion partially covered the outer surface of the core portion.

< preparation of Binder >

In a reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.15 parts of sodium lauryl sulfate (product name "Emal 2F" manufactured by Kao Corporation) as an emulsifier, and 0.5 parts of ammonium persulfate were supplied, and the gas phase portion was replaced with nitrogen gas and the temperature was raised to 60 ℃. On the other hand, 50 parts of ion-exchanged water, 0.5 part of sodium dodecylbenzenesulfonate as a dispersant, and 65 parts of 2-ethylhexyl acrylate, 30 parts of styrene, 4 parts of acrylic acid, and 1 part of allyl methacrylate as polymerizable monomers were mixed in a separate vessel to obtain a monomer mixture. This monomer mixture was continuously added to the above reactor over 4 hours to carry out polymerization. During the addition, the reaction was carried out at 60 ℃. After the completion of the addition, the reaction mixture was further stirred at 70 ℃ for 3 hours to terminate the reaction, thereby producing an aqueous dispersion containing an acrylic polymer as a binder. The glass transition temperature of the acrylic polymer was measured by the above-mentioned method, and found to be-10 ℃.

< production of slurry composition for nonaqueous Secondary Battery adhesive layer >

0.1 part of a chain saturated hydrocarbon MORESCO (registered trademark) WHITE P-350P (manufactured by MORESCO Corporation, number average molecular weight: 483) as a hydrocarbon having a molecular weight of 1000 or less, 100 parts (calculated as a solid content equivalent) of the aqueous dispersion of the above organic particles, 15 parts (calculated as a solid content equivalent) of the aqueous dispersion of the above binder, 0.15 part of a polyethylene glycol type surfactant (manufactured by SAN NOPCO LIMITED, product name "SN WET 366") as a leveling agent, 10 parts of sodium dioctyl sulfosuccinate, and water for adjusting the solid content were mixed to prepare a slurry composition for an adhesive layer having a solid content concentration of 15%. The surface tension of the resulting slurry composition was measured in accordance with the above-mentioned method.

< production of spacer >

As a spacer substrate, a polyethylene spacer substrate (thickness: 7 μm, porosity: 48%) was prepared. The obtained slurry composition for an adhesive layer was applied to one surface of the spacer base material, and then dried at 50 ℃ for 10 minutes. This operation was also performed on the reverse side, and an adhesive layer (thickness: 1 μm) was formed on both sides of the spacer base material. The thus obtained spacers each having an adhesive layer on both surfaces were evaluated for voltage resistance by the above evaluation method. The formed adhesive layer was evaluated for process adhesiveness by the above evaluation method.

< preparation of Binder for negative electrode >

33.5 parts of 1, 3-butadiene, 3.5 parts of itaconic acid, 62 parts of styrene, 1 part of 2-hydroxyethyl acrylate, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion exchange water and 0.5 part of potassium persulfate as a polymerization initiator were charged into a 5MPa pressure resistant vessel equipped with a stirrer, and after sufficient stirring, the temperature was raised to 50 ℃ to start polymerization. When the polymerization conversion reached 96%, the reaction was terminated by cooling to obtain a mixture containing a particulate binder (SBR). To the above mixture containing the granular binder, a 5% aqueous sodium hydroxide solution was added to adjust the pH to 8. Then, unreacted monomers are removed from the mixture by heating and distillation under reduced pressure, and the mixture is cooled to 30 ℃ or lower to obtain a desired aqueous dispersion containing a binder for a negative electrode.

< preparation of slurry composition for negative electrode >

100 parts of artificial graphite (volume average particle diameter: 15.6 μm) and 1 part of a 2% aqueous solution of sodium carboxymethylcellulose (MAC 350HC, manufactured by Nippon paper-making Co., Ltd.) as a thickener in terms of solid content equivalent were mixed, ion-exchanged water was further added to prepare a mixture having a solid content concentration of 68%, and the mixture was mixed at 25 ℃ for 60 minutes. Ion-exchanged water was added to the mixed solution thus obtained to prepare a solid content concentration of 62%, and then the mixture was further mixed at 25 ℃ for 15 minutes. To this mixed solution, 1.5 parts by solid content equivalent of the aqueous dispersion containing the binder for a negative electrode described above was added, ion-exchanged water was further added to adjust the final solid content concentration to 52%, and further mixed for 10 minutes. This was subjected to defoaming treatment under reduced pressure to obtain a slurry composition for a negative electrode having good fluidity.

< preparation of negative electrode >

The slurry composition for a negative electrode was applied to a copper foil having a thickness of 20 μm as a current collector by using a notch wheel coater so that the dried film thickness became about 150 μm, and was dried. The drying was carried out by conveying the copper foil at a speed of 0.5 m/min for 2 minutes in an oven at 60 ℃. Then, heat treatment was performed at 120 ℃ for 2 minutes to obtain a negative electrode raw material before pressing. The anode material before compression was rolled using a roll press, and a compressed anode having an anode active material layer thickness of 80 μm was obtained.

< preparation of slurry composition for Positive electrode >

100 parts of LiCoO having a volume average particle diameter of 12 μm as a positive electrode active material were mixed₂2 parts of acetylene black (product name "HS-100" manufactured by electrochemical Co., Ltd.) as a conductive material and 2 parts of polyvinylidene fluoride (product name "# 7208" manufactured by KUREHA Co., Ltd.) as a binder for a positive electrode in solid content equivalent, N-methylpyrrolidone was added thereto so that the total solid content concentration became 70%. These were mixed with a planetary mixer to obtain a positive electrode slurry composition.

< preparation of Positive electrode >

The slurry composition for a positive electrode was applied to an aluminum foil having a thickness of 20 μm as a current collector using a chipped wheel coater so that the dried film thickness became about 150 μm, and was dried. The drying was carried out by conveying the aluminum foil at a speed of 0.5 m/min for 2 minutes in an oven at 60 ℃. Then, the positive electrode material was heat-treated at 120 ℃ for 2 minutes to obtain a positive electrode material before pressing. The positive electrode material before pressing was rolled using a roll press to obtain a positive electrode.

< production of Secondary Battery >

Cutting the pressed positive electrode into pieces of 49 × 5cm². The positive electrode active material layer of the cut positive electrode was arranged to be cut into 55X 5.5cm²The spacer of (1). Further, the negative electrode after pressing was cut into 50X 5.2cm pieces²The cut-out negative electrode is disposed on the side opposite to the positive electrode of the separator so that the surface on the negative electrode active material layer side faces the separator. The resultant was wound by a winder to obtain a wound body. The wound body was pressed at 60 ℃ and 0.5MPa to prepare a flat body. The flat body was packed in an aluminum packaging material as a battery outer package, and an electrolyte solution (solvent: EC/DEC/VC: 68.5/30/1.5 volume ratio, electrolyte: LiPF with a concentration of 1M) was injected without leaving air₆). Further, in order to seal the opening of the aluminum packaging material, heat sealing at 150 ℃ was performed to seal the aluminum package. Thus, a 800mAh wound lithium ion secondary battery was produced. The lithium ion secondary battery thus obtained was evaluated for cycle according to the method described aboveAnd (4) characteristics.

The results of the above-described measurements or evaluations are shown in Table 1.

(example 2)

In the case of < production of slurry composition for nonaqueous secondary battery adhesive layer >, various operations, measurements and evaluations were carried out in the same manner as in example 1 except that the chain saturated hydrocarbon MORESCO (registered trademark) WHITE P-60 (manufactured by MORESCO Corporation, molecular weight: 300) was used as the hydrocarbon having a molecular weight of 1000 or less. The results are shown in Table 1.

(example 3)

Various operations, measurements and evaluations were carried out in the same manner as in example 1 except that in the case of < production of a slurry composition for a nonaqueous secondary battery adhesive layer >, octane (molecular weight: 114), which is a chain saturated hydrocarbon, was changed to a hydrocarbon having a molecular weight of 1000 or less. The results are shown in Table 1.

(example 4)

Various operations, measurements, and evaluations were performed in the same manner as in example 1 except that the amount of hydrocarbons having a molecular weight of 1000 or less was changed as shown in table 1 in < production of slurry composition for nonaqueous secondary battery adhesive layer >. The results are shown in Table 1.

(example 5)

In the case of < production of slurry composition for nonaqueous secondary battery adhesive layer >, various operations, measurements and evaluations were performed in the same manner as in example 1 except that the blending amount of sodium dioctyl sulfosuccinate was changed as shown in table 1. The results are shown in Table 1.

(example 6)

In the case of < production of slurry composition for nonaqueous secondary battery adhesive layer >, various operations, measurements and evaluations were performed in the same manner as in example 1 except that the blending amount of sodium dioctyl sulfosuccinate was changed as shown in table 1. The results are shown in Table 1.

(example 7)

In the case of < production of slurry composition for nonaqueous secondary battery adhesive layer >, various operations, measurements and evaluations were performed in the same manner as in example 1 except that the blending amount of sodium dioctyl sulfosuccinate was changed as shown in table 1. The results are shown in Table 1.

Comparative example 1

Various operations, measurements, and evaluations were performed in the same manner as in example 1 except that in the case of < production of slurry composition for nonaqueous secondary battery adhesive layer >, sulfosuccinate or a salt thereof was not added. The results are shown in Table 1.

Comparative example 2

Various operations, measurements, and evaluations were performed in the same manner as in example 1 except that in the case of < production of slurry composition for nonaqueous secondary battery adhesive layer >, hydrocarbons having a molecular weight of 1000 or less were not blended. The results are shown in Table 1.

Comparative example 3

Various operations, measurements and evaluations were carried out in the same manner as in example 1 except that 0.1 part of a hydrocarbon having a molecular weight of more than 1000 (EXCEREX (registered trademark) 15341PA, available from Mitsui chemical Co., Ltd., molecular weight: 1320) was added in place of the hydrocarbon having a molecular weight of 1000 or less in the case of < production of a slurry composition for a nonaqueous secondary battery adhesive layer >. The results are shown in Table 1.

Comparative example 4

Various operations, measurements, and evaluations were performed in the same manner as in example 1 except that in the case of < production of slurry composition for nonaqueous secondary battery adhesive layer >, hydrocarbons having a molecular weight of 1000 or less and sulfosuccinic acid esters or salts thereof were not added. The results are shown in Table 1.

In the context of table 1, the following,

"MMA" means methyl methacrylate,

"BA" means a radical of butyl acrylate,

"MAA" means methacrylic acid,

"AMA" means allyl methacrylate,

"ST" means a radical of styrene,

"2 EHA" means 2-ethylhexyl acrylate,

"AA" means acrylic acid.

[ Table 1]

As is clear from examples 1 to 7 in table 1, the separator formed using the slurry composition for a nonaqueous secondary battery adhesive layer containing organic particles, sulfosuccinate or a salt thereof, a hydrocarbon having a molecular weight of 1000 or less, and water has excellent voltage resistance. Further, it is understood from comparative examples 1 to 4 that the spacers formed using the slurry composition for a nonaqueous secondary battery adhesive layer, which lacks any of the above-described constituent components, are inferior in both voltage resistance and voltage resistance to the examples.

Industrial applicability

According to the present invention, it is possible to provide a slurry composition for an adhesive layer of a nonaqueous secondary battery, which can provide a separator having excellent voltage resistance when applied to a separator base material to form an adhesive layer.

Further, according to the present invention, it is possible to provide an adhesive layer for a nonaqueous secondary battery, which can improve the voltage resistance of a separator.

Further, according to the present invention, it is possible to provide a separator for a nonaqueous secondary battery and a nonaqueous secondary battery having excellent voltage resistance.