KR102439851B1 - Seperator for secondary battery and secondary battery including the same - Google Patents

Abstract

According to one embodiment of the present invention, in the separator for a secondary battery having a substrate and a coating layer formed on at least one surface of the substrate, the coating layer includes a binder containing an acrylic resin, and the binder containing the acrylic resin comprises: A secondary battery separator is provided, which includes a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer, and the mixing ratio of the carboxyl group-containing acrylic monomer and the acrylic acid derivative monomer is 20:80 to 80:20 in molar ratio. The binder for secondary batteries may have high heat resistance and strong adhesion, and at the same time improve cycle characteristics.

Description

Separator for secondary battery and secondary battery including same

The present invention relates to a separator for a secondary battery and a secondary battery including the same.

In recent years, as the size and weight reduction of various electronic devices progresses, secondary batteries used for power sources of these electronic devices are required to have high capacity, miniaturization, weight reduction, and the like. Among them, lithium ion secondary batteries have advantages such as high voltage, long lifespan, and high energy density. For this reason, active research on lithium ion secondary batteries is being conducted, and at the same time, they are produced and sold.

The characteristics of these lithium secondary batteries largely depend on the characteristics of the electrode, electrolyte, and other battery materials used. In particular, the separator of the lithium ion secondary battery affects the cycle characteristics of the lithium ion secondary battery.

Specifically, it is common to produce a separator by applying a slurry containing inorganic particles and a binder to a porous substrate.

Such a separator is also called a coated separator because a coating layer made of inorganic particles and a binder is formed on the porous substrate. The binder binds the inorganic particles and the porous polyethylene membrane and/or between the inorganic particles and the inorganic particles. And, when a lithium ion secondary battery is manufactured using such a separator, the cycle characteristics of the lithium ion secondary battery are between porous polyethylene (PE) and ceramic particles (a kind of inorganic particles), and between ceramic particles and ceramic particles. It depends on the properties of the binder having a binding force.

In particular, when ceramic particles having high heat resistance are used in the coating film, a battery having high voltage and high capacity characteristics can be manufactured. However, in order for the high heat-resistant ceramic particles to sufficiently exhibit their properties, it is necessary for the binder to stably maintain the structure of the ceramic coating layer during charging and discharging of the lithium ion secondary battery. In other words, it is necessary to stably keep the high heat-resistant ceramic particles in the separator. In addition, the binder is also required to firmly bind the separator and each electrode. Accordingly, a binder having excellent heat resistance and adhesive strength is in demand.

Currently, there are not many research examples regarding the binder for coating separators, and currently, there are many cases where the binder for electrodes is used for the binder for coating separators. Specifically, a binder composition in which a polyvinylidene fluoride (PVDF)-based polymer, which is a typical electrode binder, is mixed with an organic solvent such as N-methyl-2-pyrrolidone (NMP) (hereinafter referred to as “PVDF-based binder”) ) is often used as a binder for coating separators. However, there is a problem that the PVDF-based binder must be included in an excessive amount in the separator to maintain sufficient adhesion, and the stable structure of the coating layer is maintained by the impregnation of the electrolyte and the movement of lithium ions during charging and discharging of the lithium ion secondary battery. There was this troublesome problem.

As these solutions, for example, a lithium ion secondary battery with improved adhesion to an inorganic oxide (a type of inorganic particle) using a silane coupling agent and a binder having a chemical structure with strong adhesion to porous PE, or a PVDF-based polymer A method of using a binder including an IPN (interpenetrating polymer network) type resin obtained by polymerizing a hydrophilic polymer (unsaturated carboxylic acid) and the like is known.

In addition to these, a separator having a porous coating layer formed of a mixture of inorganic particles and a binder polymer on the surface of a porous substrate, and a lithium secondary battery using the separator are known (see, for example, Japanese Patent Application Laid-Open No. 2010-520095). . Japanese Patent Laid-Open Publication No. 2010-520095 discloses that butyl acrylate or a copolymer of acrylonitrile and acrylic acid is used as a binder polymer, and BaTiO ₃ or Al ₂ O ₃ is used as inorganic particles.

However, although these binders satisfy the adhesion to either the porous PE or the inorganic particles, they do not have sufficient adhesion to both the porous PE and the inorganic particles.

Therefore, when charging and discharging a lithium ion secondary battery using a coating separator using such a binder is repeated, there is a problem in that the structure of the coating layer is changed and the capacity of the battery is inevitably reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a separator for secondary batteries using a binder that has high heat resistance and strong adhesion, while at the same time improving cycle characteristics, and a secondary battery including the same. have.

In one embodiment, there is provided a separator for a secondary battery having a substrate and a coating layer formed on at least one surface of the substrate, wherein the coating layer includes a binder including an acrylic resin, and the binder including the acrylic resin includes a carboxyl group-containing acrylic monomer and Provided is a separator for a secondary battery that includes an acrylic acid derivative monomer, and a molar ratio of the carboxyl group-containing acrylic monomer and the acrylic acid derivative monomer is 20:80 to 80:20.

The carboxyl group-containing acrylic monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, monomethyl maleic acid, 2-carboxyethyl acrylate and 2-carboxyethyl methacrylate.

The acrylic acid derivative monomer may be at least one selected from the group consisting of nitrile group-containing acrylic monomers, acrylic acid esters, and acrylamides.

The nitrile group-containing acrylic monomer may be at least one selected from the group consisting of acrylonitrile, methacrylonitrile, 2-cyanoethyl acrylate and 2-cyanoethyl methacrylate.

The carboxyl group-containing acrylic monomer may include an alkali metal salt or an ammonium salt.

The coating layer may further include a water-insoluble resin.

The water-insoluble resin may include polyvinylidene fluoride, a water-insoluble acrylic resin, or a combination thereof.

The coating layer may further include polyvinyl alcohol.

The coating layer may further include inorganic particles.

The inorganic particles may include alumina, boehmite, or a combination thereof.

Another embodiment provides a secondary battery including the secondary battery separator.

The details of other implementations are included in the detailed description below.

The separator for a secondary battery according to an embodiment includes a binder including an acrylic resin as a binder of the coating layer, and the binder including the acrylic resin includes a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer, and the carboxyl group-containing acrylic monomer and the Since the mixing ratio of the acrylic acid derivative monomer is 20:80 to 80:20 in molar ratio, the binder has high heat resistance and strong adhesion.

In addition, since the binder has the above composition, cycle characteristics of the secondary battery may be improved.

Therefore, when a secondary battery is manufactured using the separator, cycle characteristics of the secondary battery can be improved.

1 is a side cross-sectional view showing the configuration of a lithium ion secondary battery according to an embodiment.
2 is a schematic diagram showing a sample used in the evaluation of heat shrinkage of an embodiment.

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

In addition, in this specification and drawings, duplicate description is abbreviate|omitted because the same code|symbol is attached|subjected to the component which has substantially the same functional structure.

Hereinafter, a separator for a secondary battery according to an embodiment will be described.

One embodiment is a separator for secondary batteries having a coating layer on at least one surface of a substrate, as a binder for forming the coating layer, and a binder composition comprising an acrylic resin having a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer in a specific mixing ratio as essential monomers. This improves the heat resistance of the separator and the adhesion between the substrate and the coating layer.

In addition, in the present invention, since the coating layer is formed using the acrylic resin as a binder, the adhesion strength between the separator and the electrode layer is improved.

That is, when the separator according to the embodiment is used, the safety and cycle life of the secondary battery are improved.

Specifically, according to one embodiment of the present invention, in the separator for secondary batteries having a substrate and a coating layer formed on at least one surface of the substrate, the coating layer includes a binder including an acrylic resin, and includes the acrylic resin The binder includes a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer, and the compounding ratio of the carboxyl group-containing acrylic monomer and the acrylic acid derivative monomer is 20:80 to 80:20 in a molar ratio. A separator for secondary batteries is provided.

The separator for secondary batteries according to an embodiment is manufactured using a binder for secondary batteries that has high heat resistance and strong adhesion, and at the same time improves cycle life.

Therefore, when a secondary battery is manufactured using the separator, cycle characteristics of the secondary battery can be improved.

Here, the carboxyl group-containing monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, monomethyl maleic acid, 2-carboxyethyl acrylate, and 2-carboxyethyl methacrylate.

In addition, the acrylic acid derivative monomer may be at least one selected from the group consisting of nitrile group-containing acrylic monomers, acrylic acid esters, and acrylamides.

In addition, the nitrile group-containing acrylic monomer may be at least one selected from the group consisting of acrylonitrile, methacrylonitrile, 2-cyanoethyl acrylate, and 2-cyanoethyl methacrylate.

In addition, the carboxyl group-containing acrylic monomer may include an alkali metal salt or an ammonium salt.

In addition, the coating layer may further include a water-insoluble resin as another binder for secondary batteries.

In addition, the water-insoluble resin may include polyvinylidene fluoride, a water-insoluble acrylic resin, or a combination thereof.

In addition, the coating layer may further include polyvinyl alcohol as another binder for secondary batteries.

In addition, the coating layer may further include inorganic particles. For example, the separator for a secondary battery according to an embodiment may further include inorganic particles. In this case, if the secondary battery is manufactured using the separator, cycle characteristics of the secondary battery can be further improved.

In addition, the inorganic particles may include alumina, boehmite, or a combination thereof.

According to another embodiment, a secondary battery including the separator is provided.

The secondary battery has excellent cycle characteristics.

As described above, the separator for secondary batteries according to one embodiment includes a binder including an acrylic resin as a binder of the coating layer, and the binder including the acrylic resin includes a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer, and contains the carboxyl group Since the mixing ratio of the acrylic monomer and the acrylic acid derivative monomer is 20:80 to 80:20 in molar ratio, the binder has high heat resistance and strong adhesion.

In addition, since the binder has the above composition, cycle characteristics of the secondary battery may be improved.

Therefore, when a secondary battery is manufactured using the separator, cycle characteristics of the secondary battery can be improved.

(First embodiment)

(Composition of lithium ion secondary battery)

First, with reference to FIG. 1, the structure of the lithium ion secondary battery 10 which concerns on 1st Embodiment is demonstrated.

The lithium ion secondary battery 10 includes a positive electrode 20, a negative electrode 30, a separator 40, and a non-aqueous electrolyte.

The charging reached voltage (oxidation-reduction potential) of the lithium ion secondary battery 10 may be, for example, 4.3V (vs.Li/Li +) or more and 5.0V or less, specifically 4.5V or more and 5.0V or less.

The form of the lithium ion secondary battery 10 is not specifically limited.

In other words, the lithium ion secondary battery 10 may be any type, such as a cylindrical shape, a prismatic shape, a laminate type, or a button type.

(Anode 20)

The positive electrode 20 includes a current collector 21 and a positive electrode active material layer 22 .

The current collector 21 may be any conductor as long as it is a conductor, and may be, for example, aluminum, stainless steel, or nickel-coated steel, but is not limited thereto.

The positive electrode active material layer 22 may include at least a positive electrode active material, and may further include a conductive material and a binder.

The positive electrode active material is, for example, a solid solution oxide containing lithium, but is not particularly limited as long as it is a material capable of electrochemically occluding and releasing lithium ions.

The solid solution oxide is, for example, Li _a Mn _x Co _y Ni _z O ₂ (1.150≤a≤1.430, 0.45≤x≤0.6, 0.10≤y≤0.15, 0.20≤z≤0.28), _{LiMnxCo y Ni z} O ₂ (0.3≤x≤0.85, 0.10≤y≤0.3, 0.10≤z≤0.3), LiMn _{1 . 5} Ni _{0 .} It becomes ₅ O ₄ .

The conductive agent is, for example, carbon black such as Ketjenblack and acetylene black, natural graphite, artificial graphite, and the like, but is not particularly limited as long as it is intended to increase the conductivity of the positive electrode.

The binder is, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber) , fluororubber, polyvinyl acetate, polymethylmethacrylate, polyethylene, cellulose nitrate, etc. As long as it is possible, it is not particularly limited.

The positive electrode active material layer 22 is produced, for example, by the following manufacturing method.

In other words, first, a positive electrode mixture is prepared by dry-mixing a positive electrode active material, a conductive agent, and a binder.

Next, a positive electrode mixture slurry is prepared by dispersing the positive electrode mixture in an appropriate organic solvent, and the positive electrode mixture slurry is applied on a current collector 21, dried and rolled to prepare a positive electrode active material layer.

(cathode 30)

The negative electrode 30 includes a current collector 31 and a negative electrode active material layer 32 .

The current collector 31 may be any conductor as long as it is a conductor, and may be, for example, aluminum, stainless steel, or nickel-plated steel, but is not limited thereto.

The negative electrode active material layer 32 may be any type as long as it is used as a negative electrode active material layer of a lithium ion secondary battery.

For example, the anode active material layer 32 may include an anode active material and further include a binder.

The negative active material is, for example, 'graphite active material (artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, etc.)', 'silicon, tin or fine particles of these oxides and graphite active material mixtures with ', 'fine particles of silicon or tin', 'alloys based on silicon or tin', and 'titanium oxide compounds such as Li ₄ Ti ₅ O ₁₂ ' it is not

The silicon oxide may be expressed as SiO _x (0≤x≤2).

Examples of the anode active material include, in addition to these, metallic lithium.

The binder may be the same as the binder constituting the cathode active material layer 22 .

The mass ratio between the positive electrode active material and the binder is not particularly limited, and the mass ratio employed in the conventional lithium ion secondary battery is applicable to this embodiment as well.

The negative electrode active material layer 32 is produced, for example, by the following manufacturing method.

In other words, first, a negative electrode mixture is prepared by dry mixing the negative electrode active material and the binder.

Next, a negative electrode mixture slurry is prepared by dispersing the negative electrode mixture in a suitable solvent, and the negative electrode mixture slurry is applied on a current collector 31, dried and rolled to produce a negative electrode active material layer 32.

(separator 40)

The separator 40 includes a substrate 40a and a coating layer (filler layer) 40b.

The substrate 40a is not particularly limited, and may be any type as long as it is used as a separator of a lithium ion secondary battery.

As the substrate 40a, it is preferable to use a porous film (porous film) or a nonwoven fabric that exhibits excellent high-rate discharge performance, either alone or in combination.

As the resin constituting the substrate 40a, for example, a polyolefin-based resin represented by polyethylene, polypropylene, etc., polyethylene terephthalate, polybutylene terephthalate, etc. Polyester resins represented by -Tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer Copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene -hexafluoropropylene (hexafluoropropylene) copolymer, vinylidene fluoride-ethylene (ethylene)-tetrafluoroethylene (tetrafluoroethylene) copolymer, etc. may be mentioned, but is not limited thereto.

The coating layer 40b may include inorganic particles and a binder.

Examples of the inorganic particles according to the present embodiment include inorganic particles having high heat resistance.

Specific examples of the inorganic particles include, but are not limited to, oxides and hydroxides of silicon, aluminum, magnesium, and titanium.

Among these, as the inorganic particles of the present embodiment, alumina, boehmite, or a combination thereof, which has particularly high heat resistance and has a low water content (water content), is particularly preferable.

By including the inorganic particles having these characteristics in the separator 40, the cycle characteristics of the lithium ion secondary battery 10 are improved.

The particle diameter of the inorganic particles is not particularly limited, and if the particle diameter of the inorganic particles used in the lithium ion secondary battery 10 is not particularly limited.

The binder holds the inorganic particles in the coating layer 40b, that is, in the separator 40.

The binder of this embodiment is an acrylic resin in which a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer are essential monomers, and these essential monomers are polymerized in a molar ratio of 20:80 to 80:20 (hereinafter referred to as "copolymerized acrylic resin") ) is included.

By using the copolymerized acrylic resin of this embodiment as a binder for the coating layer 40b, the heat resistance of the separator 40 and the adhesion between the substrate 40a and the coating layer 40b are improved.

Further, in this embodiment, by forming the coating layer 40b using the copolymerized acrylic resin as a binder, the adhesion strength between the separator 40 and the electrodes (anode 20 and cathode 30) is improved.

Thereby, the safety and cycle life of the lithium ion secondary battery 10 are improved.

From the viewpoint of further improving the heat resistance of the separator 40, the adhesion between the substrate 40a and the coating layer 40b, and the adhesion strength between the separator 40 and the electrode (anode 20 and cathode 30), the compounding ratio of the monomer containing a carboxyl group and the acrylic acid derivative monomer is It is preferably 30:70 to 70:30, more preferably 40:60 to 60:40, and most preferably 40:60 to 50:50.

In addition, the said copolymerized acrylic resin used as a main component of the binder of the coating layer 40b of this embodiment may be any of a block copolymer, a random copolymer, and a graft copolymer.

However, in order to further improve the heat resistance of the separator 40, the adhesion between the substrate 40a and the coating layer 40b, and the adhesion strength between the separator 40 and the electrode (anode 20 and cathode 30), the carboxyl group-containing acrylic monomer is polymerized in the polymer main chain, It is preferable that it is a graft copolymer in which the polymer side chain which superposed|polymerized the nitrile-group containing acrylic monomer was grafted.

In this case, the amount of moisture contained in the separator 40 can be further reduced.

Examples of the carboxyl group-containing acrylic monomer of the present embodiment include acrylic acid, methacrylic acid, maleic acid, monomethyl maleic acid, 2-carboxyethyl acrylate, and 2-carboxyethyl methacrylate.

These monomers can be used individually or in combination of two or more.

Further, examples of the acrylic acid derivative monomer of the present embodiment include nitrile group-containing acrylic monomers, acrylic acid esters, and acrylamides.

These monomers can be used individually or in combination of two or more.

Examples of the nitrile group-containing acrylic monomer include acrylonitrile, methacrylonitrile, 2-cyanoethyl acrylate, and 2-cyanoethyl methacrylate.

These monomers can be used individually or in combination of two or more.

Examples of the acrylic acid ester include isobornyl acrylate, 2,2,2-trifluoroethyl acrylate, methyl (meth)acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl. (meth)acrylic acid, hydroxyethyl acrylate, 1H, 1H-pentafluoro propyl acrylate, 2,2,3,3-tetrafluoro propyl acrylate, and the like, but are not limited thereto.

These monomers can be used individually or in combination of two or more.

Moreover, since the heat resistance of a binder becomes high, so that the glass transition temperature (Tg) of the copolymerization acrylic resin of this embodiment is high, it is preferable.

For this reason, in this embodiment, it is preferable that the glass transition temperature (Tg) of at least one of the said carboxyl group-containing acrylic monomer and the said nitrile-group containing acrylic monomer is 0 degreeC or more, and it is more preferable that it is room temperature (25 degreeC) or more.

In other words, the glass transition temperature of the entire copolymer may be high.

Moreover, when the copolymerized acrylic resin of this embodiment becomes a salt state, a glass transition temperature (Tg) will become high, and the heat resistance of a binder will become high.

For this reason, instead of or in combination with the method of increasing the glass transition temperature (Tg) of the constituent monomers of the copolymerized acrylic resin, the carboxyl group-containing acrylic monomer contains at least a part of an alkali metal salt or ammonium salt of carboxylic acid. desirable.

In addition, in order to further reduce the amount of water contained in the separator 40, it is particularly preferable that the carboxyl group-containing acrylic monomer contains at least a part of the ammonium salt of carboxylic acid.

Here, the separator 40 of the present embodiment may further contain a water-insoluble resin as a binder in addition to the copolymerized acrylic resin used as a main component.

Examples of the water-insoluble resin include polyvinylidene fluoride (PVDF) and water-insoluble acrylic resin.

These water-insoluble resins can be used individually or in combination of two or more.

As the water-insoluble acrylic resin, a resin having a molecular weight of 50000 or more is preferable, for example, poly (meth) methyl acrylate, poly (meth) butyl acrylate, poly (meth) ethyl acrylate, poly2-ethylhexyl (meth) Polyalkyl (meth)acrylate compounds, such as acrylic acid, are mentioned.

Moreover, in this embodiment, as a binder, polyvinyl alcohol (PVA) and polyvinyl acrylamide (PNVA) can be further included in addition to the said copolymerization acrylic resin used as a main component.

Said PVA and PNVA may be used instead of the said water-insoluble resin, and may be used in combination with the said water-insoluble resin.

By including the above water-insoluble resin or PVA as a binder, the heat resistance, adhesiveness, and air permeability of a binder improve further.

Therefore, by using the separator 40 produced using the binder for the lithium ion secondary battery 10, the safety and cycle characteristics of the lithium ion secondary battery 10 can be further improved.

The separator 40 is produced, for example, by the following manufacturing method.

First, an inorganic particle dispersion liquid and a binder solution are prepared.

The solvent of the inorganic particle dispersion liquid is not particularly limited as long as it can disperse the inorganic particles.

The solvent of the inorganic particle dispersion is preferably the same as the solvent of the binder solution.

The solvent of the binder solution is not particularly limited as long as it can dissolve the binder. Examples of such a solvent include N-methyl pyrrolidone (NMP) and the like.

Then, a slurry is prepared by mixing the inorganic particle dispersion liquid and the binder solution.

The slurry may be arbitrarily added such as a solvent of the binder solution, and the concentration of the inorganic particles and the binder may be adjusted.

In addition, another type of binder, for example, a PVDF-based binder (a binder containing PVDF as a main chain) may be further added to the slurry.

Then, the slurry is spread (eg, applied) on the substrate 40a, and dried to prepare a coating layer 40b. The substrate 40a may be immersed in the slurry. By these steps, the separator 40 is manufactured.

Meanwhile, in FIG. 1 , the coating layer 40b is formed only on the surface of the substrate 40a, but the coating layer 40b may also be formed in the fine holes of the substrate 40a.

As the non-aqueous electrolyte, the same non-aqueous electrolyte that has been conventionally used for lithium secondary batteries may be used without particular limitation.

The non-aqueous electrolyte may have a composition in which an electrolyte salt is contained in a non-aqueous solvent.

Examples of the non-aqueous solvent include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, and vinylene carbonate. esters; cyclic esters such as ?-butyrolactone and ?-valerolactone; chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; chain esters such as methyl formate, methyl acetate, and methyl butyric acid; Tetrahydrofuran or a derivative thereof; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane, methyl diglyme, etc. ether (ether); nitriles such as acetonitrile and benzonitrile; Dioxolane or a derivative thereof; ethylene sulfide (ethylene sulfide), sulfolane (sulfolane), sultone (sultone) or a derivative thereof alone or a mixture of two or more thereof, but is not limited thereto.

Further, as the electrolyte salt, for example, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiPF _{6 -x} (C _n F _2n+1 ) _x [provided that 1 <x <6, n=1 or 2] , LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr, KClO ₄ , KSCN, etc. 1 of lithium (Li), sodium (Na) or potassium (K) Inorganic ionic salts containing species, LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ )(C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC(C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (nC ₄ H ₉ ) ₄ NClO ₄ , (nC ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-maleate, (C ₂ H ₅ ) ₄ N Organic ionic salts such as -benzoate, (C ₂ H ₅ ) ₄ N-phtalate, stearyl sulfonic acid lithium, octyl sulfonic acid, and dodecyl benzene sulphonic acid These etc. are mentioned, These ionic compounds can be used individually or in mixture of 2 or more types.

On the other hand, the concentration of the electrolyte salt may be the same as the non-aqueous electrolyte used in the conventional lithium secondary battery, and there is no particular limitation.

In this embodiment, a non-aqueous electrolyte containing a suitable lithium compound (electrolyte salt) at a concentration of about 0.8 to 1.5 mol/L can be used.

Meanwhile, various additives may be added to the non-aqueous electrolyte.

Such additives include anode action additives, anode action additives, ester additives, carbonate ester additives, sulfuric acid ester additives, phosphoric acid ester additives, boric acid ester additives, acid anhydride additives, and electrolytes. of additives.

Any one of these may be added to the non-aqueous electrolyte, and a plurality of types of additives may be added to the non-aqueous electrolyte.

(Manufacturing method of lithium ion secondary battery)

Next, the manufacturing method of the lithium ion secondary battery 10 is demonstrated.

The anode 20 is manufactured as follows.

First, a slurry is prepared by dispersing a mixture of a positive electrode active material, a conductive agent, and a binder in a solvent (eg, N-methyl-2-pyrrolidone). Next, the slurry is spread (eg, applied) on the current collector 21 and dried to prepare a positive electrode active material layer 22.

In addition, the method of application|coating is not specifically limited. The coating method may be, for example, a knife coater (knife coater) method, a gravure coater (gravure coater) method, etc., but is not limited thereto.

Each of the following application steps may also be performed by the same method. Next, the positive electrode active material layer 22 is pressed by a press machine. Thus, the positive electrode 20 is manufactured.

The negative electrode 30 is also manufactured in the same manner as the positive electrode 20.

First, a slurry is prepared by dispersing a mixture of a negative electrode active material and a binder in a solvent (eg, N-methyl-2-pyrrolidone, water). Then, the slurry is spread on the current collector 31 (for example, For example, coating) and drying, the negative electrode active material layer 32 is manufactured. Next, the negative electrode active material layer 32 is pressed with a press machine. Thereby, the negative electrode 30 is manufactured.

The separator 40 is produced, for example, by the following manufacturing method.

In other words, first, an inorganic particle dispersion liquid and a binder solution are prepared. Then, the slurry is prepared by mixing the inorganic particle dispersion and the binder solution. The slurry may be arbitrarily added such as a solvent of the binder solution, and the concentration of the inorganic particles and the binder may be adjusted. Then, the slurry is spread (eg, applied) on the substrate 40a and dried to prepare a coating layer 40b. The substrate 40a may be immersed in the slurry. By these steps, the separator 40 is manufactured.

Then, by placing the separator 40 between the positive electrode 20 and the negative electrode 30, an electrode structure is manufactured. Then, the electrode structure is processed into a desired shape (eg, cylindrical, prismatic, laminated, button-shaped, etc.) and inserted into a container of the above shape. Next, by injecting the electrolyte solution having the above composition into the container, the pores in the separator are impregnated with the electrolyte solution. Accordingly, a lithium ion secondary battery is manufactured.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only for specifically illustrating or explaining the present invention, and the present invention is not limited thereto. In addition, since the contents not described herein can be technically inferred sufficiently by those skilled in the art, the description thereof will be omitted.

( Example )

<1. Binder Synthesis>

First, a synthesis example of the binder will be described.

In addition, the compounding ratio of sodium polyacrylate (PAANa) and another monomer described below shall represent a molar ratio unless otherwise mentioned.

Synthesis example One: Poly sodium acrylate ( PANA ) / polyacrylonitrile (PAN) = 50/50 synthesis example

After adding 363 g of distilled water and 20% aqueous sodium hydroxide solution (62.4 g, 0.9 equivalents to acrylic acid) in a 500 ml 4-neck detachable flask equipped with a stirrer, thermometer and cooling tube, the internal pressure was reduced to 10 mmHg in the diaphragm pump, and , the operation of returning the internal pressure to the normal pressure with nitrogen was repeated three times.

Next, acrylic acid (25 g, 0.347 mol), acrylonitrile (25 g, 0.471 mol), and ammonium persulfate (0.29 g, 0.00126 mol, 0.0015 equivalent) were added in a flask capable of being separated from 4 necks, and the mixture was stirred at 600 rpm.

The reaction was carried out for 4 hours while controlling heating so that the temperature of the reaction solution was stabilized between 65° C. and 70° C., after which the temperature was raised to 80° C. and reacted for 4 hours again.

After cooling to room temperature, the pH of the reaction solution was adjusted to 7 to 8 using a 20% aqueous sodium hydroxide solution.

About 2 ml of the reaction solution was dispensed and the non-volatile component (NV) was measured, and as a result, it was 11.4% (theoretical value 12%).

Synthesis example 2: Poly sodium acrylate ( PANA ) / polyacrylonitrile (PAN) = 40/60 synthesis example

456 g distilled water, 20% aqueous sodium hydroxide solution (52.7 g, 0.95 equiv relative to acrylic acid), acrylic acid (20 g, 0.278 mol), acrylonitrile (30 g, 0.565 mol), ammonium persulfate (0.29 g, 0.00126 mol, 0.0015 equiv) All were synthesized in the same manner as in Synthesis Example 1 except for using .

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was 9.3% (10% theoretical value).

Synthesis example 3: Poly meta sodium acrylate ( PANA ) / polyacrylonitrile (PAN) = 50/50 of Synthesis example

Distilled water 362 g, 20% aqueous sodium hydroxide solution (55.2 g, 0.95 equivalents based on methacrylic acid), methacrylic acid (25 g, 0.290 mol), acrylonitrile (25 g, 0.471 mol), ammonium persulfate (0.348 g, 0.00168 mol, 0.002) equivalent), all were synthesized in the same manner as in Synthesis Example 1.

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was 12.0% (theoretical value 12%).

Synthesis example 4: Poly meta sodium acrylate ( PMAANa )/ polymethacrylonitrile (PMAN)=50/50 of Synthesis example

Distilled water 362 g, 20% sodium hydroxide aqueous solution (55.2 g, 0.95 equivalents based on methacrylic acid), methacrylic acid (25 g, 0.290 mol), methacrylonitrile (25 g, 0.373 mol), ammonium persulfate (0.30 g, 0.00133 mol, 0.002 equivalent), all were synthesized in the same manner as in Synthesis Example 1.

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was 12.0% (theoretical value 12%).

Synthesis example 5: Poly sodium acrylate ( PANA )/ polyisobolyl acrylate (PIsobor)=50/50 of Synthesis example

Distilled water 205 g, 20% aqueous sodium hydroxide solution (39.5 g, 0.95 equivalents based on acrylic acid), acrylic acid (15 g, 0.208 mol), isobornyl acrylate (15 g, 0.072 mol), ammonium persulfate (0.096 g, 0.00042 mol, 0.0015) equivalent), all were synthesized in the same manner as in Synthesis Example 1.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was 12.4% (theoretical value 12.5%).

Synthesis example 6: Poly sodium acrylate ( PANA )/ Poly 2,2,2- trifluoroethyl acrylate (PTrifluoroethyl)=50/50 Synthesis example

205 g of distilled water, 20% aqueous sodium hydroxide solution (39.5 g, 0.95 equivalents based on acrylic acid), acrylic acid (15 g, 0.208 mol), 2,2,2-trifluoroethyl acrylate (15 g, 0.089 mol), ammonium persulfate ( All were synthesized in the same manner as in Synthesis Example 1 except that 0.102 g, 0.00045 mol, 0.0015 equivalent) was used.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was 12.4% (theoretical value 12.5%).

Synthesis example 7: Poly sodium acrylate ( PANA )/ Poly acrylamide ( PAAm Synthesis example of ) = 30/70

235 g of distilled water, 20% aqueous sodium hydroxide solution (11.9 g, 0.95 equiv relative to acrylic acid), acrylic acid (4.5 g, 0.062 mol), acrylamide (10.5 g, 0.148 mol), ammonium persulfate (0.048 g, 0.00021 mol, 0.001 equiv. ) was synthesized in the same manner as in Synthesis Example 1, except for using.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was 6.0% (theoretical value 6.0%).

Synthesis example 8: Poly sodium acrylate ( PANA )/ Poly acrylamide ( PAAm Synthesis example of ) = 50/50

235 g distilled water, 20% aqueous sodium hydroxide solution (19.8 g, 0.95 equiv relative to acrylic acid), acrylic acid (7.5 g, 0.104 mol), acrylamide (7.5 g, 0.106 mol), ammonium persulfate (0.048 g, 0.00021 mol, 0.001 equiv. ) was synthesized in the same manner as in Synthesis Example 1, except for using.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was 6.0% (theoretical value 6.0%).

Synthesis example 9: Poly sodium acrylate ( PANA )/ Poly acrylamide ( PAAm ) = 70/30 synthesis example

235 g distilled water, 20% aqueous sodium hydroxide solution (27.7 g, 0.95 equiv relative to acrylic acid), acrylic acid (10.5 g, 0.146 mol), acrylamide (4.5 g, 0.063 mol), ammonium persulfate (0.048 g, 0.00021 mol, 0.001 equiv. ) was synthesized in the same manner as in Synthesis Example 1, except for using.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was 6.0% (theoretical value 6.0%).

Synthesis example 10: Poly sodium acrylate ( PANA )/ Poly adamantyl acrylate (PADМ) = 62.5/37.5 of Synthesis example

89 g of distilled water in a 300 ml 4-necked separable flask equipped with a stirrer, thermometer, and cooling tube, polyvinyl alcohol as a dispersant (0.92 g, Kuraray RS2217), 20% sodium hydroxide aqueous solution (8.0 g, 0.9 with respect to acrylic acid) equivalent), the internal pressure was reduced to 10 mmHg with a diaphragm pump, and the operation of returning the internal pressure to the normal pressure with nitrogen was repeated 3 times.

Then, acrylic acid (3.2 g, 0.044 mol), adamantyl acrylate (4.8 g, 0.027 mol), and ammonium persulfate (0.023 g, 0.00011 mol, 0.0015 equiv) were added in a four-necked separable flask, and the mixture was stirred at 600 rpm.

The reaction solution was reacted for 4 hours while controlling the heating so that the temperature of the reaction solution was stably controlled between 65° C. and 70° C., the temperature was raised to 80° C., and the reaction was continued for 4 hours.

After cooling to room temperature, the pH of the reaction solution was adjusted to 7 to 8 using a 25% aqueous ammonia solution.

About 2 ml of the reaction solution was dispensed and the nonvolatile component (NV) was measured. As a result, it was found to be 9.0% (10% theoretical value).

Synthesis example 11: Poly sodium acrylate ( PANA )/ Poly adamantyl acrylate (PADМ) = 70/30 of Synthesis example

93 g distilled water, 20% aqueous sodium hydroxide solution (9.7 g, 0.9 equivalents relative to acrylic acid), acrylic acid (3.89 g, 0.054 mol), adamantyl acrylate (4.34 g, 0.024 mol), ammonium persulfate (0.027 g, 0.00012 mol) , 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 10.

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was found to be 8.9% (10% theoretical value).

Synthesis example 12: Poly sodium acrylate ( PANA )/ Poly adamantyl acrylate (PADМ) = 80/20 of Synthesis example

86 g distilled water, 20% aqueous sodium hydroxide solution (11.2 g, 0.9 equivalents relative to acrylic acid), acrylic acid (4.48 g, 0.062 mol), adamantyl acrylate (2.80 g, 0.016 mol), ammonium persulfate (0.027 g, 0.00012 mol) , 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 10.

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was found to be 8.9% (10% theoretical value).

Synthesis example 13: Poly sodium acrylate ( PANA )/ Poly t-butyl acrylate (P-t-BuA) = 70/30 of Synthesis example

In a 300ml 4-neck detachable flask equipped with a stirrer, thermometer, and cooling tube, distilled water 81g, 20% aqueous sodium hydroxide solution (9.7g, 0.9 equivalents based on acrylic acid) and acrylic acid (3.8g, 0.054mol) were added, and then the diaphragm The operation of reducing the internal pressure to 10 mmHg with the pump and returning the internal pressure to the normal pressure with nitrogen was repeated 3 times.

Then, t-butyl acrylate (3.08 g, 0.024 mol) and ammonium persulfate (0.027 g, 0.00012 mol, 0.0015 equiv) were added in a four-necked separable flask, and the mixture was stirred at 600 rpm.

The reaction was carried out for 4 hours while controlling heating so that the temperature of the reaction solution was stabilized between 65° C. and 70° C., after which the temperature was raised to 80° C. and reacted for 4 hours again.

After cooling to room temperature, the pH of the reaction solution was adjusted to 7 to 8 using a 25% aqueous ammonia solution.

About 2 ml of the reaction solution was dispensed and the nonvolatile component (NV) was measured. As a result, it was found to be 9.0% (10% theoretical value).

Synthesis example 14: Poly sodium acrylate ( PANA )/ Poly t-Butyl acrylate (P-t-BuA) = 80/20 Synthesis example

79 g distilled water, 20% aqueous sodium hydroxide solution (11.2 g, 0.9 equivalents relative to acrylic acid), acrylate (4.48 g, 0.062 mol), t-butyl acrylate (2.05 g, 0.016 mol), ammonium persulfate (0.027 g, 0.00012) mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 13.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was found to be 9.0% (10% theoretical value).

Synthesis example 15: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly -2-methylpropane sulfonate sodium ( PAMPS ) = 20/60/20 Synthesis example )

145 g distilled water, 20% aqueous sodium hydroxide solution (9.0 equiv based on the total amount of acrylic acid and 2-methyl propane sulfonic acid), acrylate (3.0 g, 0.042 mol), ammonium persulfate (0.077 g, 0.00034 mol, 0.0015 equiv), t -All were synthesized in the same manner as in Synthesis Example 13, except that acrylonitrile (9.0 g, 0.170 mol) and 2-methyl propane sulfonic acid (3.0 g, 0.014 mol) were used instead of -butyl acrylate.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was found to be 9.0% (10% theoretical value).

Synthesis example 16: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly -2-methylpropane sulfonate sodium ( PAMPS ) = 30/60/10 Synthesis example

147 g distilled water, 20% aqueous sodium hydroxide solution (11.1 g, 0.8 equiv relative to acrylic acid), acrylate (4.5 g, 0.062 mol), acrylonitrile (9.0 g, 0.170 mol), 2-methylpropane sulfonate sodium (1.5 g, 0.007 mol) and ammonium persulfate (0.082 g, 0.00036 mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 15.

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was found to be 8.9% (10% theoretical value).

Synthesis example 17: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly -2-methylpropane sulfonate sodium ( PAMPS ) = 35/60/5 Synthesis example

148 g distilled water, 20% aqueous sodium hydroxide solution (12.2 g, 0.8 equiv relative to acrylic acid), acrylate (5.25 g, 0.073 mol), acrylonitrile (9.0 g, 0.170 mol), 2-methylpropane sulfonate sodium (0.75 g, 0.004 mol) and ammonium persulfate (0.084 g, 0.00037 mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 15.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was found to be 9.0% (10% theoretical value).

Synthesis example 18: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly -2-methylpropane sulfonate sodium ( PAMPS ) = 25/55/20 Synthesis example

147 g distilled water, 20% aqueous sodium hydroxide solution (10.6 g, 0.8 equiv relative to acrylic acid), acrylate (3.75 g, 0.052 mol), acrylonitrile (8.25 g, 0.155 mol), 2-methylpropane sulfonate sodium (3.0 g, 0.014 mol) and ammonium persulfate (0.076 g, 0.00033 mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 15.

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was found to be 8.8% (10% theoretical value).

Synthesis example 19: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly -2-methylpropane sulfonate sodium ( PAMPS ) = 35/55/10 Synthesis example

149 g distilled water, 20% aqueous sodium hydroxide solution (12.8 g, 0.8 equiv relative to acrylic acid), acrylate (5.25 g, 0.073 mol), acrylonitrile (8.25 g, 0.155 mol), 2-methylpropane sulfonate sodium (1.5 g, 0.007 mol) and ammonium persulfate (0.081 g, 0.00035 mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 15.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was found to be 9.0% (10% theoretical value).

Synthesis example 20: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly -2-methylpropane sulfonate sodium ( PAMPS ) = of 40/55/5 Synthesis example

150 g distilled water, 20% aqueous sodium hydroxide solution (13.9 g, 0.8 equiv relative to acrylic acid), acrylate (6.0 g, 0.083 mol), acrylonitrile (8.25 g, 0.155 mol) sodium 2-methylpropanesulfonate (0.75 g, 0.004) mol) and ammonium persulfate (0.083 g, 0.00036 mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 15.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was found to be 9.0% (10% theoretical value).

Synthesis example 21: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly disodium maleate ( PMalNa ) = 38/57/5 Synthesis example

143 g of distilled water, 20% aqueous sodium hydroxide solution (14.2 g, 0.8 equivalents based on twice the total moles of acrylic acid and maleic acid), acrylic acid (5.40 g, 0.075 mol), acrylonitrile (8.10 g, 0.153 mol), maleic acid All were synthesized in the same manner as in Synthesis Example 15 except that an acid (0.69 g, 0.007 mol) and ammonium persulfate (0.08 g, 0.00035 mol, 0.0015 equivalent) were used.

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was found to be 8.8% (10% theoretical value).

Synthesis example 22: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly Acryloisobutyl POSS (P-i- BuPOSS ) = of 40/45/15 Synthesis example

149 g distilled water, 20% aqueous sodium hydroxide solution (13.3 g, 0.8 equiv relative to acrylic acid), acrylic acid (6.00 g, 0.083 mol), acrylonitrile (6.75 g, 0.127 mol), polyacryloisobutyl POSS (2.25 g, 0.0024) mol) and ammonium persulfate (0.073 g, 0.00032 mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 15.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was found to be 9.0% (10% theoretical value).

Synthesis example 23: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly Acryloisobutyl POSS (P-i- BuPOSS ) = 40/50/10 Synthesis example

149 g distilled water, 20% aqueous sodium hydroxide solution (13.3 g, 0.8 equiv relative to acrylic acid), acrylic acid (6.00 g, 0.083 mol), acrylonitrile (7.50 g, 0.141 mol), polyacryloisobutyl POSS (1.50 g, 0.0016) mol) and ammonium persulfate (0.077 g, 0.00034 mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 15.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was found to be 9.0% (10% theoretical value).

Synthesis example 24: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN)/ Poly Acryloisobutyl POSS (P-i- BuPOSS ) = of 40/55/5 Synthesis example

150 g distilled water, 20% aqueous sodium hydroxide solution (13.3 g, 0.8 equiv relative to acrylic acid), acrylic acid (6.00 g, 0.083 mol), acrylonitrile (8.25 g, 0.155 mol), polyacryloisobutyl POSS (0.75 g, 0.0008) mol) and ammonium persulfate (0.082 g, 0.00036 mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 15.

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was found to be 8.9% (10% theoretical value).

Synthesis example 25: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN) = 30/70 Synthesis example

147 g distilled water, 20% aqueous sodium hydroxide solution (11.2 g, 0.9 equivalents relative to acrylic acid), acrylic acid (4.5 g, 0.062 mol), acrylonitrile (10.5 g, 0.198 mol), ammonium persulfate (0.089 g, 0.00039 mol, 0.0015) equivalent), all were synthesized in the same manner as in Synthesis Example 1.

However, as the reaction proceeded, a large amount of aggregates were precipitated, so that it could not be used as a binder for producing a separator.

Synthesis example 26: Poly sodium acrylate ( PANA )/ Poly Acrylonitrile (PAN) = 80/20 Synthesis example

167 g distilled water, 20% aqueous sodium hydroxide solution (30.0 g, 0.9 equivalents relative to acrylic acid), acrylic acid (12.0 g, 0.167 mol), acrylonitrile (3.0 g, 0.057 mol), ammonium persulfate (0.076 g, 0.00033 mol, 0.0015) equivalent), all were synthesized in the same manner as in Synthesis Example 1.

As a result of measuring the non-volatile component (NV) of the reaction solution, it was found to be 9.0% (10% theoretical value).

Synthesis example 27: Poly sodium acrylate ( PANA )/ Poly Butyl Acrylic rate (P-n-Bu)/poly Glish dill meta krill rate ( PGryci ) = 11/86/3 of Synthesis example

181 g distilled water, 20% aqueous sodium hydroxide solution (5.2 g, 0.9 equiv relative to acrylic acid), acrylic acid (2.10 g, 0.029 mol), butyl acrylate (16.8 g, 0.131 mol), glycidyl methacrylate (0.6 g, 0.004 mol) ) and ammonium persulfate (0.056 g, 0.00036 mol, 0.0015 equivalent) were all synthesized in the same manner as in Synthesis Example 15.

As a result of measuring the nonvolatile component (NV) of the reaction solution, it was found to be 8.9% (10% theoretical value).

<2. coating separator Production>

comparative example One

Boehmite C20 (manufactured by TAIMEI CHEMICALS CO., LTD.) 61.4g, boehmite ACTILOX-200SM (manufactured by Navaltech) 168g in distilled water, 10% sodium polyacrylate aqueous solution (Aldrich) Co., Ltd., 68.3 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) was added, stirred until it became a slurry, and then a bead mill (zirconia beads, 0.5?, filling rate 60%, 2000rpm, 4 passes) to prepare a boehmite/binder mixed solution.

Then, the above-mentioned boehmite was applied to a commercially available 12 μm thick polyethylene microporous membrane (T12-507 <manufactured by SK Innovation>) using a gravure coater prepared so that the application amount (loading amount) after drying was 3.0 g/m ² . The coating separator of Comparative Example 1 was obtained by applying and drying the /binder mixed solution.

Furthermore, vacuum drying (133 Pa) was performed at 60 degreeC for 12 hours, and the thing from which water|moisture content was removed was used for battery manufacture.

comparative example 2

Except for using 175 g of distilled water and 27.2 g of a 25wt% PVDF dispersion (Solvay's Solef90000) (NV conversion 6.8g, 10% by weight based on the total weight of boehmite) as a binder, in the same manner as in Comparative Example 1, Comparative Example 2 of coated separator was obtained.

Example One

Except for using 171 g of distilled water and the binder prepared in Synthesis Example 1 (59.9 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite), the coating separator of Example 1 was prepared in the same manner as in Comparative Example 1 got it

Example 2

158 g of distilled water and the binder prepared in Synthesis Example 2 (73.4 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were all carried out in the same manner as in Comparative Example 1, and the coated separator of Example 2 was prepared got it

Example 3

175 g of distilled water and the binder prepared in Synthesis Example 3 (73.4 g, NV conversion 6.8 g, 10 wt% based on the total weight of boehmite) were all carried out in the same manner as in Comparative Example 1, and the coated separator of Example 3 was prepared got it

Example 4

175 g of distilled water and the binder prepared in Synthesis Example 4 (56.9 g, NV conversion 6.8 g, 10 wt% based on the total weight of boehmite) were all carried out in the same manner as in Comparative Example 1, and the coated separator of Example 4 was prepared got it

Example 5

Except for using 177 g of distilled water and the binder prepared in Synthesis Example 5 (55.0 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite), the coating separator of Example 5 was prepared in the same manner as in Comparative Example 1 got it

Example 6

The coated separator of Example 6 was prepared in the same manner as in Comparative Example 1 except that 177 g of distilled water and the binder prepared in Synthesis Example 6 (55.0 g, NV conversion 6.8 g, 10 wt% based on the total weight of boehmite) were used. got it

Example 7

The coated separator of Example 7 was prepared in the same manner as in Comparative Example 1 except that 118 g of distilled water and the binder prepared in Synthesis Example 7 (113.8 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 8

The coated separator of Example 8 was prepared in the same manner as in Comparative Example 1 except that 118 g of distilled water and the binder prepared in Synthesis Example 8 (113.8 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 9

The coated separator of Example 9 was prepared in the same manner as in Comparative Example 1 except that 118 g of distilled water and the binder prepared in Synthesis Example 9 (113.8 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 10

Distilled water 188 g, the binder prepared in Synthesis Example 1 (29.9 g, NV conversion 3.4 g, 5 wt % based on the total weight of boehmite), and a 25 wt % PVDF water dispersion (Solvay Co., Ltd. Solef 90000, 13.7 g, NV conversion 3.4) g, 5% by weight relative to the total weight of boehmite) was carried out in the same manner as in Comparative Example 1, except that a coated separator of Example 10 was obtained.

Example 11

Distilled water 188 g, the binder prepared in Synthesis Example 2 (36.7 g, NV conversion 3.4 g, 5 wt % based on the total weight of boehmite), and a 25 wt % PVDF water dispersion (Solvay Co., Ltd. Solef 90000, 13.7 g, NV conversion 3.4) g, 5% by weight relative to the total weight of boehmite) was carried out in the same manner as in Comparative Example 1, except that a coated separator of Example 11 was obtained.

Example 12

Distilled water 182 g, the binder prepared in Synthesis Example 1 (29.9 g, NV conversion 3.4 g, 5 wt % based on the total weight of boehmite), and 16.9 wt % of a water-insoluble acrylic water dispersion (Hitachi Chemical Company, Ltd) SSE2G manufactured by Company, 20.2 g, NV conversion 3.4 g, 5% by weight based on the total weight of boehmite) was carried out in the same manner as in Comparative Example 1 to obtain a coated separator of Example 12.

Example 13

174 g of distilled water, the binder prepared in Synthesis Example 2 (36.7 g, NV conversion 3.4 g, 5 wt % based on the total weight of boehmite), and 16.9 wt % of a water-insoluble acrylic water dispersion (Hitachi Chemical Company, Ltd) SSE2G manufactured by Company, 20.2 g, NV conversion 3.4 g, 5 wt% based on the total weight of boehmite) was carried out in the same manner as in Comparative Example 1, to obtain a coated separator of Example 13.

Example 14

The coated separator of Example 14 was prepared in the same manner as in Comparative Example 1 except that 157 g of distilled water and the binder prepared in Synthesis Example 10 (75.6 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 15

The coated separator of Example 15 was prepared in the same manner as in Comparative Example 1 except that 156 g of distilled water and the binder prepared in Synthesis Example 11 (76.4 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 16

The coated separator of Example 16 was prepared in the same manner as in Comparative Example 1 except that 156 g of distilled water and the binder prepared in Synthesis Example 12 (76.4 g, NV conversion 6.8 g, 10 wt% based on the total weight of boehmite) were used. got it

Example 17

Except for using 157 g of distilled water and the binder prepared in Synthesis Example 13 (75.6 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite), the coating separator of Example 17 was prepared in the same manner as in Comparative Example 1 got it

Example 18

The coated separator of Example 18 was prepared in the same manner as in Comparative Example 1 except that 157 g of distilled water and the binder prepared in Synthesis Example 14 (75.6 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 19

The coated separator of Example 19 was prepared in the same manner as in Comparative Example 1 except that 157 g of distilled water and the binder prepared in Synthesis Example 15 (75.6 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 20

The coated separator of Example 20 was prepared in the same manner as in Comparative Example 1 except that 156 g of distilled water and the binder prepared in Synthesis Example 16 (76.4 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 21

The coated separator of Example 21 was prepared in the same manner as in Comparative Example 1 except that 157 g of distilled water and the binder prepared in Synthesis Example 17 (75.6 g, NV conversion 6.8 g, 10 wt% based on the total weight of boehmite) were used. got it

Example 22

The coated separator of Example 22 was prepared in the same manner as in Comparative Example 1 except that 155 g of distilled water and the binder prepared in Synthesis Example 18 (77.3 g, NV conversion 6.8 g, 10 wt % based on the total weight of boehmite) were used. got it

Example 23

The coated separator of Example 23 was prepared in the same manner as in Comparative Example 1 except that 157 g of distilled water and the binder prepared in Synthesis Example 19 (75.6 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 24

The coated separator of Example 24 was prepared in the same manner as in Comparative Example 1 except that 157 g of distilled water and the binder prepared in Synthesis Example 20 (75.6 g, NV conversion 6.8 g, 10 wt% based on the total weight of boehmite) were used. got it

Example 25

The coated separator of Example 25 was prepared in the same manner as in Comparative Example 1 except that 155 g of distilled water and the binder prepared in Synthesis Example 20 (77.3 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 26

A coated separator of Example 26 was obtained in the same manner as in Comparative Example 1 except that 157 g of distilled water and the binder prepared in Synthesis Example 21 (75.6 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. .

Example 27

The coated separator of Example 27 was prepared in the same manner as in Comparative Example 1 except that 157 g of distilled water and the binder prepared in Synthesis Example 22 (75.6 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

Example 28

The coated separator of Example 28 was prepared in the same manner as in Comparative Example 1 except that 156 g of distilled water and the binder prepared in Synthesis Example 20 (76.4 g, NV conversion 6.8 g, 10 wt% based on the total weight of boehmite) were used. got it

comparative example 3

The coated separator of Comparative Example 3 was prepared in the same manner as in Comparative Example 1 except that 157 g of distilled water and the binder prepared in Synthesis Example 26 (75.6 g, NV conversion 6.8 g, 10 wt% based on the total weight of boehmite) were used. got it

comparative example 4

The coated separator of Comparative Example 4 was prepared in the same manner as in Comparative Example 1 except that 159 g of distilled water and the binder prepared in Synthesis Example 27 (73.1 g, NV conversion 6.8 g, 10% by weight based on the total weight of boehmite) were used. got it

<3. Evaluation of adhesion of coating layer>

An adhesive tape (Nichiban Co., Ltd. Cello Tape (registered trademark) No. 405) having a width of 1.5 cm was attached to the coated separator fixed on the stainless plate.

And the peeling strength at the time of 180 degree peeling was measured using the peeling tester (SHIMAZU EZ-S by Shimadzu Corporation).

The adhesive evaluation result was put together in following Table 1, and was shown.

<4. heat shrink Rating>

As shown in Fig. 2, the coated separator was cut out so that TD*MD=60mm*80mm, and marks were placed at intervals of 50mm using a nogis (vernier caliper) in the TD/MD direction.

The separator was sandwiched between the folded aluminum foils and left still in a thermostat at 130°C for 60 minutes.

After taking out the separator, the interval of each display of TD/MD was read with a nogis (vernier caliper), and the thermal contraction rate was computed according to following formula (1).

The heat shrinkage evaluation results are collectively shown in Table 1 below.

In addition, in the following formula (1), the space|interval in TD direction was used for the space|interval after heating.

[Equation 1]

Heat shrinkage (%)=((50-interval after heating)/50)*100)

<4-1. air permeability Rating>

The air permeability was evaluated by measuring the permeation time of 100 cc of air in a Gurley-type densometer manufactured by Toyo Seiki (internal cylinder weight (pressure) 567 g, permeation surface pore diameter of 28.6 mm (6.45 square centimeters)).

The shorter the permeation time, the higher the air permeability.

bookbinder coated separator Peel strength (mN/mm) Shrinkage (%) permeability
(sec/100cc) PANA Comparative Example 1 450 1.5 335 PVDF Comparative Example 2 5 3 105 Synthesis Example 26 Comparative Example 3 400 2 225 Synthesis Example 27 Comparative Example 4 110 22 254 Synthesis Example 1 Example 1 270 2 227 Synthesis Example 2 Example 2 353 2 225 Synthesis Example 3 Example 3 234 1.5 261 Synthesis Example 4 Example 4 318 2 251 Synthesis Example 5 Example 5 230 2 174 Synthesis Example 6 Example 6 201 1.5 223 Synthesis Example 7 Example 7 351 1.5 290 Synthesis Example 8 Example 8 514 2 318 Synthesis Example 9 Example 9 412 1.5 320 Synthesis Example 1: Solef90000
=5:5 Example 10 160 1.5 101 Synthesis Example 2: solef90000
=5:5 Example 11 120 1.5 105 Synthesis Example 1: SSE2G
=5:5 Example 12 167 1.5 101 Synthesis Example 2: SSE2G
=5:5 Example 13 123 1.5 103 Synthesis Example 10 Example 14 320 2 210 Synthesis Example 11 Example 15 310 1.5 215 Synthesis Example 12 Example 16 280 1.5 220 Synthesis Example 13 Example 17 230 2 210 Synthesis Example 14 Example 18 200 1.5 220 Synthesis Example 15 Example 19 194 1.5 213 Synthesis Example 16 Example 20 324 1.5 221 Synthesis Example 17 Example 21 462 1.5 222 Synthesis Example 18 Example 22 350 1.5 227 Synthesis Example 19 Example 23 447 1.5 225 Synthesis Example 20 Example 24 562 1.5 218 Synthesis Example 21 Example 25 350 1.5 264 Synthesis Example 22 Example 26 270 1.5 271 Synthesis Example 23 Example 27 382 1.5 280 Synthesis Example 24 Example 28 330 1.5 254

According to Table 1, it can be seen that the binders obtained by adding a water-insoluble resin to the binders of Synthesis Examples 1 to 24, Synthesis Examples 26 and 27 and the binders of Synthesis Examples 1 and 2 are excellent in heat resistance and adhesion. have.

In addition, it can be seen that these binders also have low air permeability.

<5. Secondary Battery Manufacturing>

Example 29

(Preparation of negative electrode mixture slurry)

By mixing 96 mass % of artificial graphite, 2 mass % of acetylene black, 1 mass % of styrene butadiene copolymer (SBR) binder, and 1 mass % of carboxymethyl cellulose (CMC), adding water to the mixture for viscosity adjustment, negative electrode A mixture slurry was prepared.

On the other hand, the non-volatile component in the negative electrode mixture slurry was 48 mass % with respect to the total mass of the slurry.

(Production of cathode)

Then, the gap of the bar coater is adjusted so that the amount of the mixture applied after drying (area density) is 9.55 mg/cm ² , and the negative electrode mixture slurry is uniformly applied to the copper foil (current collector, thickness 10 μm) by this bar coater. did.

Next, the negative electrode mixture slurry was dried for 15 minutes with a blow dryer set at 80°C.

Next, the dried negative electrode mixture was pressed with a roll press so that the density of the mixture was 1.65 g/cm ³ .

Then, the negative electrode mixture was vacuum dried at 150° C. for 6 hours to prepare a sheet-shaped negative electrode comprising a negative electrode current collector and a negative electrode active material layer.

(Preparation of positive electrode mixture slurry)

Solid solution oxide Li _{1 . 20} Mn _{0 . 55} Co _{0 . 10} Ni _{0 .} A positive electrode mixture slurry was formed by dispersing 96 mass% of ₁₅ O ₂ , 2 mass% of Ketjen Black, and 2 mass% of polyvinylidene fluoride in N-methyl-2-pyrrolidone.

On the other hand, the non-volatile component in the positive electrode mixture slurry was 50 mass % based on the total mass of the slurry.

(production of anode)

Next, the gap of the bar coater was adjusted so that the mixed coating amount (area density) after drying was 22.7 mg/cm ² , and with this bar coater, the positive electrode mixture slurry was applied onto the aluminum current collector foil serving as the current collector.

Then, the positive electrode mixture slurry was dried for 15 minutes with a blow dryer set at 80°C.

Next, the dried positive electrode mixture was pressed with a roll press so that the density of the mixture was 3.9 g/cm ³ .

Then, the positive electrode mixture was vacuum dried at 80° C. for 6 hours to prepare a sheet-shaped positive electrode comprising a positive electrode current collector and a positive electrode active material layer.

(Production of lithium ion secondary battery)

The negative electrode shown in the negative electrode preparation example was cut into a circle having a diameter of 1.55 cm, and the positive electrode shown in the positive electrode preparation example was cut into a circle having a diameter of 1.3 cm.

Next, the coated separator prepared in Example 1 was cut into a circle having a diameter of 1.8 cm.

In a stainless steel coin outer container with a diameter of 2.0 cm, the positive electrode cut into a circle with a diameter of 1.3 cm, the coated separator of Example 1 cut into a circle with a diameter of 1.8 cm, the negative electrode cut into a circle with a diameter of 1.55 cm, and as a spacer Copper foil with a thickness of 200 μm cut into a circle with a diameter of 1.5 cm was stacked in this order.

Then, 150 L of electrolyte solution (1.4 M LiPF ₆ ethylene carbonate/diethyl carbonate/fluoroethylene carbonate = 10/70/20 mixed solution (volume ratio)) was added to the container.

Next, the polypropylene packing was interposed, the cap made of stainless steel was put on the container, and the container was sealed with the bonding machine for coin battery production.

Thereby, the lithium ion secondary battery (coin cell) which concerns on Example 14 was produced.

Example 30 to 56; comparative example 5 and 6

Lithium ion secondary batteries according to Examples 30 to 56 and Comparative Examples 5 to 8 were produced in the same manner as in Example 29 except that the separator shown in Table 2 was used.

<6. Evaluation of cycle life>

Lithium ion secondary batteries according to Examples and Comparative Examples were charged and discharged once at 25°C and 0.2C.

Thereafter, a charge-discharge cycle of charging and discharging the lithium ion secondary battery at 1.0 C was repeated 100 times.

The discharge capacity retention ratio (percentage) was calculated by dividing the discharge capacity at 100 cycles (100th of a 1.0C charge/discharge cycle) by the discharge capacity at one cycle (1st of a 1.0C charge/discharge cycle).

The higher the capacity retention ratio, the better the cycle life.

The evaluation results are aggregated and shown in Table 2 below.

coin cell separator Capacity retention rate after 100 cycles Example 29 Example 1 87 Example 30 Example 2 89 Example 31 Example 3 88 Example 32 Example 4 90 Example 33 Example 5 89 Example 34 Example 6 90 Example 35 Example 7 91 Example 36 Example 8 92 Example 37 Example 9 93 Example 38 Example 10 94 Example 39 Example 11 95 Example 40 Example 12 96 Example 41 Example 13 97 Example 42 Example 14 92 Example 43 Example 15 93 Example 44 Example 16 92 Example 45 Example 17 90 Example 46 Example 18 90 Example 47 Example 19 92 Example 48 Example 20 91 Example 49 Example 21 93 Example 50 Example 22 93 Example 51 Example 23 93 Example 52 Example 24 91 Example 53 Example 25 91 Example 54 Example 26 91 Example 55 Example 27 92 Example 56 Example 28 91 Comparative Example 5 Comparative Example 1 80 Comparative Example 6 Comparative Example 2 85 Comparative Example 7 Comparative Example 3 90 Comparative Example 8 Comparative Example 4 70

According to Table 2, it can be seen that the cycle characteristics of the lithium ion secondary battery according to the present embodiment are improved. Moreover, when water-insoluble resin is added as a binder, it turns out that cycling characteristics are especially improved.

On the other hand, the separator of Comparative Example 1 had good peel strength and shrinkage, but the secondary battery using the separator of Comparative Example 1 had low cycle characteristics. This is considered to be because the air permeability of Comparative Example 1 was high, and moisture remained in the separator.

Therefore, it turns out that even if it uses as a binder the acrylic resin obtained by polymerizing only the carboxyl group-containing acrylic monomer (for example, the sodium polyacrylate of Comparative Example 1), it turns out that cycling characteristics cannot be improved.

In other words, it can be seen that in order to synthesize a binder capable of improving cycle characteristics, it is necessary to include not only the carboxyl group-containing acrylic monomer but also the acrylic acid derivative monomer as an essential monomer.

As a result, the binder according to the present embodiment can improve high heat resistance and strong adhesion, and at the same time, improve cycle characteristics.

Therefore, by manufacturing the separator 40 using the binder which concerns on this embodiment, and manufacturing the lithium ion secondary battery 10 using this separator 40, the cycling characteristics of the lithium ion secondary battery 10 can be improved.

In addition, since thermal contraction of the separator 10 is also suppressed, thermal runaway of the lithium ion secondary battery 10 can be suppressed, and furthermore, the safety of the lithium ion secondary battery 10 is improved.

Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It belongs to the scope of the right of the invention.

For example, in the above embodiment, the binder according to the present embodiment is used for the lithium ion secondary battery, but the binder according to the present embodiment may be used for other types of secondary batteries.

10 Li-ion secondary battery
20 anode
21 positive current collector
22 cathode active material layer
30 cathode
31 Anode current collector
32 Anode active material layer
40 separator
40a
40b coating layer

Claims (11)

In the separator for a secondary battery having a substrate and a coating layer formed on at least one surface of the substrate,
The coating layer includes a binder containing an acrylic resin,
The binder containing the acrylic resin includes a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer,
A secondary battery separator in a molar ratio of 30:70 to 70:30 in a molar ratio of the carboxyl group-containing acrylic monomer and the acrylic acid derivative monomer. According to claim 1,
The carboxyl group-containing acrylic monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, monomethyl maleic acid, 2-carboxyethyl acrylate and 2-carboxyethyl methacrylate. According to claim 1,
The acrylic acid derivative monomer is at least one selected from the group consisting of nitrile group-containing acrylic monomers, acrylic acid esters and acrylamides. 4. The method of claim 3,
The nitrile group-containing acrylic monomer is at least one selected from the group consisting of acrylonitrile, methacrylonitrile, 2-cyanoethyl acrylate and 2-cyanoethyl methacrylate. According to claim 1,
The carboxyl group-containing acrylic monomer is a secondary battery separator comprising an alkali metal salt or an ammonium salt. According to claim 1,
The secondary battery separator further comprising a water-insoluble resin in the coating layer. 7. The method of claim 6,
The water-insoluble resin is a secondary battery separator comprising polyvinylidene fluoride, a water-insoluble acrylic resin, or a combination thereof. According to claim 1,
The secondary battery separator further comprising the coating layer polyvinyl alcohol. According to claim 1,
The coating layer is a secondary battery separator further comprising inorganic particles. 10. The method of claim 9,
The inorganic particle is a secondary battery separator comprising alumina, boehmite, or a combination thereof. A secondary battery comprising the separator for a secondary battery according to any one of claims 1 to 10.

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