KR20160061260A - Seperator for secondary battery and secondary battery including the same - Google Patents

Abstract

The purpose of the present invention is to provide a separator for a secondary battery using a binder for improving cycle characteristics while simultaneously having high heat resistance and strong adhesion; and a secondary battery including the same. According to an embodiment of the present invention, provided is a separator for a secondary battery, which includes a substrate and a coating layer formed on at least one surface of the substrate. The coating layer includes a binder including acrylic resin. The binder including the acrylic resin includes carboxyl group-containing acryl monomers and acrylic acid derivative monomers. The carboxyl group-containing acryl monomers and the acrylic acid derivative monomers are mixed at a molar ratio of 20:80 to 80:20. The binder for a secondary battery has high heat resistance and strong adhesion, and can simultaneously improve cycle characteristics.

Description

TECHNICAL FIELD [0001] The present invention relates to a separator for a secondary battery, and a secondary battery including the same. BACKGROUND ART [0002]

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

2. Description of the Related Art Recently, with the progress of miniaturization and weight reduction of various electronic devices, secondary batteries used for power supply of these electronic devices are required to have higher capacity, smaller size, and lighter weight. Among them, lithium ion secondary batteries have advantages such as high voltage, long lifetime and high energy density. For this reason, active researches on lithium ion secondary batteries have been conducted, and they have been produced and sold at the same time.

The characteristics of these lithium secondary batteries are largely determined by the properties of electrodes, electrolytic solutions, and other battery materials used. Particularly, the separator of the lithium ion secondary battery affects the cycle characteristics of the lithium ion secondary battery.

Specifically, a separator is generally produced by applying a slurry containing inorganic particles and a binder to a porous substrate.

Such a separator is also called a coating separator because a coating layer composed of inorganic particles and a binder is formed on a porous substrate. The binder binds the inorganic particles and the porous polyethylene film and / or the inorganic particles and the inorganic particles. When the lithium ion secondary battery is fabricated using such a separator, the cycle characteristics of the lithium ion secondary battery are determined by the relationship between the porous polyethylene (PE) and the ceramic particles (one kind of inorganic particles), and also between the ceramic particles and the ceramic particles Of the binder.

Particularly, when ceramic particles having high heat resistance are used for a coating film, a battery having high voltage and high capacity characteristics can be produced. However, in order for the high heat-resistant ceramic particles to fully 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 maintain the high heat-resistant ceramic particles in the separator. It is also necessary that the binder be firmly bonded to the separator and each electrode. Therefore, there is a demand for a binder having excellent heat resistance and adhesion.

At present, there are not many examples of a binder for a coating separator, and at the present time, a binder for an electrode is often used for a binder for a coating separator. Specifically, a binder composition obtained by mixing a polyvinylidene fluoride (PVDF) -based polymer as a typical electrode binder with an organic solvent such as N-methyl-2-pyrrolidone (NMP) (hereinafter referred to as "PVDF binder" ) Is often used for a binder for a coating separator. However, there is a problem that the PVDF binder needs to be contained in an excessive amount in the separator in order to maintain a sufficient adhesive strength, and the stable structure of the coating layer due to the impregnation of the electrolyte and the mass transfer of lithium ions during charging and discharging of the lithium ion secondary battery There was a problem that this was difficult.

As such a solution, for example, a lithium ion secondary battery having improved adhesion to an inorganic oxide (a kind of inorganic particles) using a binder and a silane coupling agent having a strong chemical bonding with porous PE, a PVDF polymer And a binder containing an IPN (interpenetrating polymer network) resin in which a hydrophilic polymer (unsaturated carboxylic acid) is polymerized 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 (for example, see JP-A-2010-520095) . Japanese Patent Application Laid-Open 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, these binders satisfy the adhesive force to either the porous PE or the inorganic particles, but do not have a sufficient adhesive force to both the porous PE and the inorganic particles.

Therefore, if the charging and discharging of the lithium ion secondary battery using the coating separator using such a binder is repeated, there is a problem that the structure of the coating layer changes and the capacity of the battery decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a separator for a secondary battery and a secondary battery including the same, which have a high heat resistance and a strong adhesive force, have.

One embodiment is a separator for a secondary battery comprising a base material and a coating layer formed on at least one surface of the base material, wherein the coating layer comprises a binder containing an acrylic resin, the binder containing the acrylic resin comprises a carboxyl group- Acrylic acid derivative monomer, wherein the mixing ratio of the carboxyl group-containing acrylic monomer and the acrylic acid derivative monomer is 20:80 to 80:20 in a molar ratio.

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 comprising the secondary battery separator.

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

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

Further, by having the above-mentioned composition, the binder can improve the cycle characteristics of the secondary battery.

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

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

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

In the specification and drawings, the same reference numerals are given to constituent elements having substantially the same functional configuration, and redundant description will be omitted.

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

One embodiment is a separator for a secondary battery having a coating layer on at least one surface of a substrate, wherein 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 is used as a binder for forming the coating layer Whereby the heat resistance of the separator and the adhesion between the substrate and the coating layer are improved.

Further, 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 one embodiment is used, safety and cycle life of the secondary battery are improved.

Specifically, according to an embodiment of the present invention, there is provided a separator for a secondary battery comprising a substrate and a coating layer formed on at least one surface of the substrate, wherein the coating layer comprises a binder containing an acrylic resin, Wherein the binder contains 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 a molar ratio.

The separator for a secondary battery according to an embodiment is manufactured by using a binder for a secondary battery having high heat resistance and strong adhesion and at the same time, improving the cycle life.

Therefore, when the secondary battery is manufactured using the separator, the 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.

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 a secondary battery.

Further, 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 as another binder for the secondary battery.

Further, 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, when the secondary battery is manufactured using the separator, the 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, there is provided a secondary battery including the separator.

The secondary battery has excellent cycle characteristics.

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

Further, by having the above-mentioned composition, the binder can improve the cycle characteristics of the secondary battery.

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

(First Embodiment)

(Configuration of Lithium Ion Secondary Battery)

First, the configuration of the lithium ion secondary battery 10 according to the first embodiment will be described with reference to Fig.

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 (redox potential) of the lithium ion secondary battery 10 may be, for example, 4.3 V (vs. Li / Li +) to 5.0 V or less, specifically 4.5 V or more and 5.0 V or less.

The shape of the lithium ion secondary battery 10 is not particularly limited.

In other words, the lithium ion secondary battery 10 may be any of a cylindrical type, a rectangular type, a laminate type, a button type, and the like.

(Anode 20)

The anode 20 includes a current collector 21 and a cathode active material layer 22.

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

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

The cathode 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 occluding and releasing lithium ions electrochemically.

The solid solution oxides include 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), LiMn _x Co _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 . 5} O ₄ .

The conductive agent is, for example, carbon black such as Ketjenblack, acetylene black, natural graphite, artificial graphite or the like, but is not particularly limited as long as it enhances the conductivity of the anode.

The binder may include, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, Fluororubber, polyvinyl acetate, polymethylmethacrylate, polyethylene, cellulose nitrate and the like. However, the positive electrode active material and the conductive material may be adhered onto the current collector 21 And is not particularly limited as long as it can.

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

In other words, first, a cathode mixture is prepared by dry mixing the cathode active material, the conductive agent, and the binder.

Then, a positive electrode mixture slurry is prepared by dispersing the positive electrode mixture in an appropriate organic solvent, and the positive electrode active material layer is formed by applying the positive electrode mixture slurry to the current collector 21, followed by drying and rolling.

(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, and may be, for example, aluminum, stainless steel, and nickel-plated steel, but is not limited thereto.

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

For example, the negative electrode active material layer 32 includes a negative electrode active material, and may further include a binder.

Examples of the negative electrode active material include graphite active materials (artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, etc.), silicon, tin or microparticles of these oxides and graphite active material , An alloy containing silicon or tin as a base material, and a titanium oxide-based compound such as Li ₄ Ti ₅ O ₁₂ , and the like, but are not limited thereto It is not.

The oxide of silicon may be represented by SiO _x (0? _X ? 2).

Examples of the negative electrode active material include metal lithium and the like.

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

The mass ratio of the positive electrode active material to the binder is not particularly limited, and the mass ratio employed in the conventional lithium ion secondary battery is also applicable to the present embodiment.

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

In other words, first, the negative electrode active material and the binder are dry-mixed to prepare the negative electrode mixture.

Then, the negative electrode mixture slurry is prepared by dispersing the negative electrode mixture in an appropriate solvent, and the negative electrode mixture slurry is coated on the current collector 31, followed by drying and rolling to form the 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 any material may be used as long as it is used as a separator of a lithium ion secondary battery.

As the base material 40a, it is preferable to use a porous film (porous film) or nonwoven fabric exhibiting excellent high rate discharge performance singly or in combination.

Examples of the resin constituting the substrate 40a include polyolefin resins represented by polyethylene, polypropylene, etc., polyethylene terephthalate, polybutylene terephthalate and the like (PVDF), vinylidene fluoride (VDF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride - tetrafluoroethylene copolymers, vinylidene fluoride-trifluoroethylene copolymers, vinylidene fluoride-fluoroethylene copolymers, vinylidene fluoride-hexafluoroacetone copolymers, vinylidene fluoride- A vinylidene fluoride-ethylene copolymer, a vinylidene fluoride-propylene copolymer, a vinylidene fluoride-tri A vinylidene fluoride copolymer, a fluoro propylene copolymer, a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, a vinylidene fluoride-ethylene copolymer, a tetrafluoroethylene copolymer, And the like, but the present invention 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 such inorganic particles include, but are not limited to, oxides of silicon, aluminum, magnesium, titanium, and hydroxides thereof.

Of these, alumina, boehmite, or a combination thereof is particularly preferable as the inorganic particles of the present embodiment, particularly having high heat resistance and having a small water content (moisture content).

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

The particle size of the inorganic particles is not particularly limited and is not particularly limited as long as it is the particle size of the inorganic particles used in the lithium ion secondary battery 10.

The binder is to hold the inorganic particles in the coating layer 40b, that is, in the separator 40. [

The binder of this embodiment is an acrylic resin (hereinafter referred to as " copolymerized acrylic resin ") obtained by polymerizing an essential monomer and a necessary monomer in a molar ratio of 20:80 to 80:20 with a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer as essential monomers ).

By using the copolymer 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 the present embodiment, the coating layer 40b is formed using the copolymer acrylic resin as a binder, whereby the adhesion strength between the separator 40 and the electrodes (the anode 20 and the cathode 30) is improved.

As a result, 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 and the adhesion between the substrate 40a and the coating layer 40b and the adhesion strength between the separator 40 and the electrodes (the anode 20 and the cathode 30), the mixing ratio of the monomer containing a carboxyl group and the monomer of the acrylic acid derivative is in a molar ratio More preferably from 30:70 to 70:30, even more preferably from 40:60 to 60:40, and most preferably from 40:60 to 50:50.

The copolymer acrylic resin to be the main component of the binder of the coating layer 40b of the present 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 base material 40a and the coating layer 40b, and the adhesion strength between the separator 40 and the electrodes (the anode 20 and the cathode 30), the polymer main chain, It is preferable that the graft copolymer is a graft copolymer in which polymer side chains obtained by polymerization of a nitrile group-containing acrylic monomer are grafted.

In this case, the water content 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, 2-carboxyethyl methacrylate and the like.

These monomers may be used singly or in combination.

Examples of the acrylic acid derivative monomer of the present embodiment include a nitrile group-containing acrylic monomer, acrylic acid ester, and acrylamide.

These monomers may be used singly or in combination.

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

These monomers may be used singly or in combination.

Examples of the acrylic esters include isobornyl acrylate, 2,2,2-trifluoroethyl acrylate, methyl (meth) acrylate, butyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (Meth) acrylic acid, hydroxyethyl acrylate, 1H, 1H-pentafluoropropyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, and the like, but are not limited thereto.

These monomers may be used singly or in combination.

The higher the glass transition temperature (Tg) of the copolymer acrylic resin of the present embodiment is, the higher the heat resistance of the binder is.

Therefore, in the present embodiment, at least one of the carboxyl group-containing acrylic monomer and the nitrile group-containing acrylic monomer preferably has a glass transition temperature (Tg) of 0 ° C or higher, more preferably room temperature (25 ° C) or higher.

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

In addition, when the copolymerized acrylic resin of the present embodiment is in a salt state, the glass transition temperature (Tg) is high and the heat resistance of the binder is high.

Accordingly, instead of the method of increasing the glass transition temperature (Tg) of the constituent monomers of the copolymer acrylic resin, or in combination with the method, the acrylic monomer containing a part of the carboxylic acid-containing acrylic monomer or the ammonium salt of the carboxylic acid desirable.

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 partially contains an ammonium salt of carboxylic acid.

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

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

These water-insoluble resins may be used singly or in combination.

The water-insoluble acrylic resin is preferably a resin having a molecular weight of 50,000 or more, and examples thereof include poly (methyl methacrylate), poly (methyl methacrylate), poly (methyl methacrylate) (Meth) acrylate compounds such as acrylic acid.

In addition, in the present embodiment, as the binder, polyvinyl alcohol (PVA) and polyvinyl acrylamide (PNVA) may be further included in addition to the copolymer acrylic resin used as the main component.

The PVA and PNVA may be used in place of the water-insoluble resin, or may be used in combination with the water-insoluble resin.

By including the above-described water-insoluble resin or PVA as a binder, the heat resistance, adhesion, and breathability of the binder are further improved.

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

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

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

The solvent of the inorganic particle dispersion 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-methylpyrrolidone (NMP) and the like.

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

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

Further, another kind of binder such as a PVDF binder (a binder containing PVDF as a main chain) may be further added to the slurry.

Then, the slurry is developed (for example, coated) on the substrate 40a and dried to prepare a coating layer 40b. The substrate 40a may be immersed in the slurry. By these processes, the separator 40 is manufactured.

On the other hand, although the coating layer 40b is formed only on the surface of the substrate 40a in FIG. 1, the coating layer 40b may also be formed in the thin hole of the substrate 40a.

The nonaqueous electrolyte solution may be any nonaqueous electrolytic solution that can be conventionally used for a lithium secondary battery, without any particular limitation.

The non-aqueous electrolyte may have a composition containing an electrolyte salt in a non-aqueous solvent.

Examples of the non-aqueous solvent include cyclic carbonates such as propylene carbonate, ethylene carbonate, ethylene 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 butyric acid methyl; Tetrahydrofuran or a derivative thereof; Dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane, methyl diglyme, etc. Ether; Nitriles such as acetonitrile and benzonitrile; Dioxolane or a derivative thereof; Ethylene sulfide, sulfolane, sultone or a derivative thereof, or a mixture of two or more thereof, but the present invention is not limited thereto.

The electrolyte salt may be LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ or LiPF _{6 -x} (C _n F _{2n + 1} ) _x (where 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, 1 of lithium (Li), sodium (Na) or potassium (K), such as KSCN an inorganic ion salt 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 ion salts such as benzoate, (C ₂ H ₅ ) ₄ N-phthalate, stearyl sulfonic acid lithium, octyl sulfonic acid, and dodecyl benzene sulphonic acid These ionic compounds may be used singly or in combination of two or more.

On the other hand, the concentration of the electrolyte salt may be the same as that of the non-aqueous electrolyte used in the conventional lithium secondary battery, and is not particularly limited.

In the present embodiment, a nonaqueous electrolyte solution containing a suitable lithium compound (electrolyte salt) at a concentration of about 0.8 to 1.5 mol / L can be used.

On the other hand, various additives may be added to the non-aqueous electrolyte.

Examples of such an additive include an anode active additive, an anode active additive, an ester additive, a carbonic acid ester additive, a sulfate ester additive, a phosphate ester additive, a borate ester additive, an acid anhydride additive, And the like.

Any one of them may be added to the nonaqueous electrolyte solution, or a plurality of kinds of additives may be added to the nonaqueous electrolyte solution.

(Manufacturing Method of Lithium Ion Secondary Battery)

Next, a method of manufacturing the lithium ion secondary battery 10 will be described.

The anode 20 is fabricated as follows.

First, a slurry is prepared by dispersing a mixture of a cathode active material, a conductive agent, and a binder in a solvent (for example, N-methyl-2-pyrrolidone). Subsequently, the slurry is developed (for example, coated) on the collector 21 and dried to prepare the positive electrode active material layer 22.

On the other hand, the method of application is not particularly limited. As a coating method, for example, a knife coater method, a gravure coater method, or the like may be used, but the present invention is not limited thereto.

Each of the following coating processes can also be carried out by the same method. Then, the cathode active material layer 22 is pressed by a press machine. Thus, the anode 20 is manufactured.

The negative electrode 30 is also made the same 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 (for example, N-methyl-2-pyrrolidone, water) And then dried to produce a negative electrode active material layer 32. Subsequently, the negative electrode active material layer 32 is pressed by a pressing machine.

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

In other words, first, an inorganic particle dispersion 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 optionally added with a solvent such as a binder solution, and the concentration of the inorganic particles and the binder may be adjusted. Then, the coating layer 40b is prepared by developing (for example, applying) the slurry on the substrate 40a and drying the slurry. The substrate 40a may be immersed in the slurry. By these processes, the separator 40 is produced.

Then, the separator 40 is placed between the anode 20 and the cathode 30 to produce an electrode structure. Next, the electrode structure is processed into a desired shape (e.g., cylindrical shape, square shape, laminate shape, button shape, etc.) and inserted into the container of the above-described shape. Subsequently, by injecting the electrolyte solution of the above composition into the container, the electrolyte solution is impregnated into each pore in the separator. Thus, a lithium ion secondary battery is manufactured.

Hereinafter, specific embodiments of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto. In addition, contents not described here can be inferred sufficiently technically if they are skilled in the art, and a description thereof will be omitted.

( Example )

<1. Binder synthesis>

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

On the other hand, the blending ratio of sodium polyacrylate (PAANa) described below and other monomers is expressed as a molar ratio unless otherwise stated.

Synthetic example  One: Poly  Sodium acrylate ( PAANA ) / Polyacrylonitrile (PAN) = 50/50

363 g of distilled water and 20% sodium hydroxide aqueous solution (62.4 g, 0.9 equivalents with respect to acrylic acid) were added to a 500 mL four-neck separable flask equipped with a stirrer, a thermometer and a cooling tube, and then the pressure inside the diaphragm pump was reduced to 10 mmHg , And the operation of returning the internal pressure to atmospheric pressure with nitrogen was repeated three times.

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 to the four-neck separable flask and stirred at 600 rpm.

The reaction was allowed to proceed for 4 hours while the heating was controlled so that the temperature of the reaction liquid was stabilized between 65 ° C and 70 ° C, after which the temperature was raised to 80 ° C and reacted for another 4 hours.

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

About 2 ml of the reaction solution was taken out, and the nonvolatile component (NV) was measured to be 11.4% (theoretical value 12%).

Synthetic example  2: Poly  Sodium acrylate ( PAANA ) / Polyacrylonitrile (PAN) = 40/60

(0.29 g, 0.00126 mol, 0.0015 eq.) Of distilled water, 456 g of 20% sodium hydroxide aqueous solution (52.7 g, 0.95 eq. Relative to acrylic acid), acrylic acid (20 g, 0.278 mol), acrylonitrile Were synthesized in the same manner as in Synthesis Example 1. [

The non-volatile component (NV) of the reaction solution was measured to be 9.3% (theoretical value 10%).

Synthetic example  3: Poly Meta  Sodium acrylate ( PAANA ) / Polyacrylonitrile (PAN) = 50/50 Synthetic example

(35.2 g, 0.471 mol), acrylonitrile (25 g, 0.471 mol) and ammonium persulfate (0.348 g, 0.00168 mol, 0.002 mol) were added to a mixture of 362 g of distilled water, 55.2 g of 20% sodium hydroxide solution, 0.95 equivalent of methacrylic acid, Equivalent) was used in place of the compound represented by the formula (1).

The nonvolatile component (NV) of the reaction solution was measured and found to be 12.0% (theoretical value 12%).

Synthetic example  4: Poly Meta  Sodium acrylate ( PMAANa ) / Polymethacrylonitrile (PMAN) = 50/50 Synthetic example

, Methacrylic acid (25g, 0.290mol), methacrylonitrile (25g, 0.373mol), ammonium persulfate (0.30g, 0.00133mol, 0.353mol), distilled water (36.2g), 20% sodium hydroxide aqueous solution (55.2g, 0.95 equivalents relative to methacrylic acid) 0.002 eq.) Were used in place of the compound (1).

The nonvolatile component (NV) of the reaction solution was measured and found to be 12.0% (theoretical value 12%).

Synthetic example  5: Poly  Sodium acrylate ( PAANA ) / Polyisobornyl acrylate (PIsobor) = 50/50 Synthetic example

(15 g, 0.072 mol), ammonium persulfate (0.096 g, 0.00042 mol, 0.0015 mol), 20 g of a 20% sodium hydroxide aqueous solution (39.5 g, 0.95 equivalent based on acrylic acid) Equivalent) was used in place of the compound represented by the formula (1).

The nonvolatile component (NV) of the reaction solution was measured and found to be 12.4% (theoretical value 12.5%).

Synthetic example  6: Poly  Sodium acrylate ( PAANA ) / Poly  2,2,2- Trifluoroethyl acrylate (PTrifluoroethyl) = 50/50 Synthetic example

(15 g, 0.089 mol), 2,2,2-trifluoroethylacrylate (15 g, 0.089 mol) and ammonium persulfate (15 g, 0.208 mol) 0.102 g, 0.00045 mol, 0.0015 eq.).

The nonvolatile component (NV) of the reaction solution was measured and found to be 12.4% (theoretical value 12.5%).

Synthetic example  7: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylamide ( PAAm ) = 30/70

(0.049 g, 0.00021 mol, 0.001 eq.) Was added to a mixture of 235 g of distilled water, 20% sodium hydroxide aqueous solution (11.9 g, 0.95 equivalent based on acrylic acid), acrylic acid (4.5 g, 0.062 mol), acrylamide ) Were used in place of the compound (1).

The nonvolatile component (NV) of the reaction solution was measured and found to be 6.0% (theoretical value 6.0%).

Synthetic example  8: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylamide ( PAAm ) = 50/50 Synthesis Example

(7.5 g, 0.106 mol), ammonium persulfate (0.048 g, 0.00021 mol, 0.001 eq.), Distilled water (23.8 g), 20% aqueous sodium hydroxide solution (19.8 g, 0.95 equivalents relative to acrylic acid) ) Were used in place of the compound (1).

The nonvolatile component (NV) of the reaction solution was measured and found to be 6.0% (theoretical value 6.0%).

Synthetic example  9: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylamide ( PAAm ) = 70/30 Synthesis Example

(27.5 g, 0.95 equivalents based on acrylic acid), acrylic acid (10.5 g, 0.146 mol), acrylamide (4.5 g, 0.063 mol) and ammonium persulfate (0.048 g, 0.00021 mol, 0.001 eq. ) Were used in place of the compound (1).

The nonvolatile component (NV) of the reaction solution was measured and found to be 6.0% (theoretical value 6.0%).

Synthetic example  10: Poly  Sodium acrylate ( PAANA ) / Poly Adamantil Acrylate  (PADM) = 62.5 / 37.5 Synthetic example

In a 300 ml four-neck separable flask equipped with a stirrer, a thermometer and a condenser tube, 89 g of distilled water, 0.92 g of polyvinyl alcohol (RS2217 manufactured by Kuraray Co., Ltd.) as a dispersant, 20% aqueous solution of sodium hydroxide , The pressure inside was reduced to 10 mmHg with a diaphragm pump, and the operation of returning the internal pressure to the atmospheric pressure with nitrogen was repeated three 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 equivalent) were added to the four-neck separable flask and stirred at 600 rpm.

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

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

About 2 ml of the reaction solution was taken out and the nonvolatile component (NV) was measured to be 9.0% (theoretical value 10%).

Synthetic example  11: Poly  Sodium acrylate ( PAANA ) / Poly Adamantil Acrylate  (PADM) = 70/30 Synthetic example

(4.7 g, 0.024 mol) and ammonium persulfate (0.027 g, 0.00012 mol) were added to a mixture of 93 g of distilled water, an aqueous 20% sodium hydroxide solution (9.7 g, 0.9 equivalent based on acrylic acid), acrylic acid (3.89 g, 0.054 mol), adamantyl acrylate , 0.0015 eq.) Were used as the starting materials.

The nonvolatile component (NV) of the reaction solution was measured and found to be 8.9% (theoretical value 10%).

Synthetic example  12: Poly  Sodium acrylate ( PAANA ) / Poly Adamantil Acrylate  (PAD M) = 80/20 Synthetic example

(2.8 g, 0.016 mol) and ammonium persulfate (0.027 g, 0.00012 mol) were added to a mixture of distilled water (86 g), 20% sodium hydroxide aqueous solution (11.2 g, 0.9 equivalent based on acrylic acid), acrylic acid (4.48 g, 0.062 mol), adamantyl acrylate , 0.0015 eq.) Were used as the starting materials.

The nonvolatile component (NV) of the reaction solution was measured and found to be 8.9% (theoretical value 10%).

Synthetic example  13: Poly  Sodium acrylate ( PAANA ) / Poly  t-butyl Acrylate  (P-t-BuA) = 70/30 Synthetic example

81 g of distilled water, an aqueous solution of 20% sodium hydroxide (9.7 g, 0.9 equivalent to acrylic acid) and acrylic acid (3.8 g, 0.054 mol) were added to a four-neck separable flask of 300 ml equipped with a stirrer, a thermometer and a cooling tube, The internal pressure was reduced to 10 mmHg with a pump, and the operation of returning the internal pressure to normal pressure with nitrogen was repeated three times.

Then, t-butyl acrylate (3.08 g, 0.024 mol) and ammonium persulfate (0.027 g, 0.00012 mol, 0.0015 equivalent) were added to the four-neck separable flask and stirred at 600 rpm.

The reaction was allowed to proceed for 4 hours while controlling the heating so that the temperature of the reaction liquid was stabilized between 65 ° C and 70 ° C, after which the temperature was raised to 80 ° C and reacted for another 4 hours.

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

About 2 ml of the reaction solution was taken out and the nonvolatile component (NV) was measured to be 9.0% (theoretical value 10%).

Synthetic example  14: Poly  Sodium acrylate ( PAANA ) / Poly  t-butyl Acrylate  (P-t-BuA) = 80/20 Synthetic example

Butyl acrylate (2.05 g, 0.016 mol), ammonium persulfate (0.027 g, 0.00012 mol), distilled water (79 g), 20% sodium hydroxide aqueous solution (11.2 g, 0.9 equivalent relative to acrylic acid) mol, 0.0015 eq.).

The nonvolatile component (NV) of the reaction solution was measured and found to be 9.0% (theoretical value 10%).

Synthetic example  15: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly -2-methylpropanesulfonic acid sodium ( PAMPS ) = 20/60/20 Synthetic example )

(0.077 g, 0.00034 mol, 0.0015 equivalent), 20 g of sodium hydroxide solution (0.8 equivalent based on the total amount of 9.0 acrylic acid and 2-methylpropanesulfonic acid), acrylate (3.0 g, 0.042 mol) Was synthesized in the same manner as in Synthesis Example 13 except that acrylonitrile (9.0 g, 0.170 mol) and 2-methylpropanesulfonic acid (3.0 g, 0.014 mol) were used in place of butyl acrylate.

The nonvolatile component (NV) of the reaction solution was measured and found to be 9.0% (theoretical value 10%).

Synthetic example  16: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly -2-methylpropanesulfonic acid sodium ( PAMPS ) = 30/60/10 Synthetic example

(4.5 g, 0.062 mol), acrylonitrile (9.0 g, 0.170 mol) and sodium 2-methylpropanesulfonate (1.5 g, 0.16 mol) were added to a mixture of 147 g of distilled water, 20% sodium hydroxide aqueous solution (11.1 g, 0.007 mol) and ammonium persulfate (0.082 g, 0.00036 mol, 0.0015 equivalent), respectively.

The nonvolatile component (NV) of the reaction solution was measured and found to be 8.9% (theoretical value 10%).

Synthetic example  17: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly -2-methylpropanesulfonic acid sodium ( PAMPS ) = 35/60/5 Synthetic example

(12.2 g, 0.8 equivalent to acrylic acid), acrylate (5.25 g, 0.073 mol), acrylonitrile (9.0 g, 0.170 mol), sodium 2-methylpropanesulfonate (0.75 g, 0.004 mol) and ammonium persulfate (0.084 g, 0.00037 mol, 0.0015 equivalent), respectively.

The nonvolatile component (NV) of the reaction solution was measured and found to be 9.0% (theoretical value 10%).

Synthetic example  18: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly -2-methylpropanesulfonic acid sodium ( PAMPS ) = 25/55/20 Synthetic example

(10.6 g, 0.8 equivalent to acrylic acid), acrylate (3.75 g, 0.052 mol), acrylonitrile (8.25 g, 0.155 mol), sodium 2-methylpropanesulfonate (3.0 g, 0.014 mol) and ammonium persulfate (0.076 g, 0.00033 mol, 0.0015 eq.) Were used.

The nonvolatile component (NV) of the reaction solution was measured and found to be 8.8% (theoretical value 10%).

Synthetic example  19: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly -2-methylpropanesulfonic acid sodium ( PAMPS ) = 35/55/10 Synthetic example

(12.5 g, 0.8 equivalent to acrylic acid), acrylate (5.25 g, 0.073 mol), acrylonitrile (8.25 g, 0.155 mol) and sodium 2-methylpropanesulfonate (1.5 g, 0.007 mol) and ammonium persulfate (0.081 g, 0.00035 mol, 0.0015 equivalent), respectively.

The nonvolatile component (NV) of the reaction solution was measured and found to be 9.0% (theoretical value 10%).

Synthetic example  20: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly -2-methylpropanesulfonic acid sodium ( PAMPS ) = 40/55/5 Synthetic example

(0.75 g, 0.004 moles) was added to a mixture of 150 g of distilled water, 20% sodium hydroxide aqueous solution (13.9 g, 0.8 equivalent based on acrylic acid), acrylate (6.0 g, 0.083 mol), acrylonitrile (8.25 g, 0.155 mol) mol) and ammonium persulfate (0.083 g, 0.00036 mol, 0.0015 eq.) were used.

The nonvolatile component (NV) of the reaction solution was measured and found to be 9.0% (theoretical value 10%).

Synthetic example  21: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly  Disodium maleate ( PMalNa ) = 38/57/5 Synthetic example

143 g of distilled water, 14.2 g of a 20% sodium hydroxide aqueous solution, 0.8 equivalent of 2 equivalents of the total molar amount of acrylic acid and maleic acid, acrylic acid (5.40 g, 0.075 mol), acrylonitrile (8.10 g, 0.153 mol) (0.69 g, 0.007 mol) and ammonium persulfate (0.08 g, 0.00035 mol, 0.0015 eq.).

The nonvolatile component (NV) of the reaction solution was measured and found to be 8.8% (theoretical value 10%).

Synthetic example  22: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly  Acryloyl isobutyl POSS  (P-i- BuPOSS ) = 40/45/15 Synthetic example

(13.3 g, 0.8 equivalent 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 eq.).

The nonvolatile component (NV) of the reaction solution was measured and found to be 9.0% (theoretical value 10%).

Synthetic example  23: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly  Acryloyl isobutyl POSS  (P-i- BuPOSS ) = 40/50/10 Synthetic example

(13.0 g, 0.8 equivalent to acrylic acid), acrylic acid (6.00 g, 0.083 mol), acrylonitrile (7.50 g, 0.141 mol) and polyacryloisobutyl POSS (1.50 g, 0.0016 mol) and ammonium persulfate (0.077 g, 0.00034 mol, 0.0015 equivalent) were used in place of the ammonium persulfate.

The nonvolatile component (NV) of the reaction solution was measured and found to be 9.0% (theoretical value 10%).

Synthetic example  24: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) / Poly  Acryloyl isobutyl POSS  (P-i- BuPOSS ) = 40/55/5 Synthetic example

(13.3 g, 0.8 equivalent 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 used.

The nonvolatile component (NV) of the reaction solution was measured and found to be 8.9% (theoretical value 10%).

Synthetic example  25: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) = 30/70 Synthetic example

(0.029 g, 0.00039 mol, 0.0015 mol) were added to a mixture of 147 g of distilled water, 20% sodium hydroxide aqueous solution (11.2 g, 0.9 equivalent relative to acrylic acid), acrylic acid (4.5 g, 0.062 mol), acrylonitrile Synthesis Example 1] was used instead of the compound (1).

However, as the reaction proceeded, a large amount of the aggregate was precipitated, so that it could not be used as a binder for separator production.

Synthetic example  26: Poly  Sodium acrylate ( PAANA ) / Poly  Acrylonitrile (PAN) = 80/20 Synthetic example

(30.0 g, 0.9 equivalent based on acrylic acid), acrylic acid (12.0 g, 0.167 mol), acrylonitrile (3.0 g, 0.057 mol) and ammonium persulfate (0.076 g, 0.00033 mol, 0.0015 Synthesis Example 1] was used instead of the compound (1).

The nonvolatile component (NV) of the reaction solution was measured and found to be 9.0% (theoretical value 10%).

Synthetic example  27: Poly  Sodium acrylate ( PAANA ) / Poly  Butyl acrylate Rate  (P-n-Bu) / poly Glycia  Deal Meta  Krill Rate  ( PGryci ) = 11/86/3 Synthetic example

(2.1 g, 0.029 mol), butyl acrylate (16.8 g, 0.131 mol) and glycidyl methacrylate (0.6 g, 0.004 mol) were added to a mixture of 181 g of distilled water, 5.2 g of sodium hydroxide aqueous solution (0.9 equivalent of acrylic acid) ) And ammonium persulfate (0.056 g, 0.00036 mol, 0.0015 eq.), Respectively.

The nonvolatile component (NV) of the reaction solution was measured and found to be 8.9% (theoretical value 10%).

<2. coating Separator  Production>

Comparative Example  One

164 g of distilled water and 61 g of a 10% aqueous solution of sodium polyacrylate (Aldrich) were added to 61.4 g of boehmite C20 (manufactured by TAIMEI CHEMICALS CO., LTD.) And 6.8 g of boehmite ACTILOX-200SM (Zirconia beads, 0.5?, Packing rate of 60%, 2000 rpm, and the like) were added to the mixture, and the mixture was stirred until the mixture became a slurry. 4 times) to prepare a boehmite / binder mixed solution.

Then, a commercially available 12 μm thick polyethylene microporous membrane (T12-507 (manufactured by SK Innovation), which was prepared by using a gravure coater prepared to have a coating amount (loading amount) after drying of 3.0 g / m ² , / Binder mixed solution was applied and dried to obtain a coating separator of Comparative Example 1. [

Vacuum drying (133 Pa) was carried out at 60 占 폚 for 12 hours, and water was removed and used for battery production.

Comparative Example  2

175 g of distilled water and 27.2 g of a 25 wt% PVDF dispersion (Solef 90000 from Solvay) (6.8 g in terms of NV, 10 wt% with respect to the total weight of boehmite) as a binder were used in Comparative Example 2 Of a coating separator.

Example  One

171 g of distilled water and 59.9 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 1 were used in place of the coating separator of Example 1, .

Example  2

Except that 158 g of distilled water and 73.4 g (6.8 g in terms of NV) of the binder (10 wt% based on the total weight of boehmite) prepared in Synthesis Example 2 were used, and the coating separator of Example 2 .

Example  3

Except that 175 g of distilled water and 73.4 g (6.8 g in terms of NV, 10 wt% with respect to the total weight of boehmite) of the binder prepared in Synthesis Example 3 were used, and the coating separator of Example 3 .

Example  4

Except that 175 g of distilled water and 56.9 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 4 were used, and the coating separator of Example 4 was used .

Example  5

177 g of distilled water, 55.0 g of the binder prepared in Synthesis Example 5 (6.8 g in terms of NV, 10% by weight based on the total weight of the boehmite) were used in the same manner as in Comparative Example 1 to prepare a coating separator of Example 5 .

Example  6

177 g of distilled water and 55.0 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 6 were used in place of the coating separator of Example 6, .

Example  7

Except that 118 g of distilled water and 113.8 g (6.8 g in terms of NV) of the binder (10 wt% based on the total weight of boehmite) prepared in Synthesis Example 7 were used, and the coating separator of Example 7 .

Example  8

Except that 118 g of distilled water and 113.8 g (6.8 g in terms of NV, 10 wt% with respect to the total weight of boehmite) of the binder prepared in Synthesis Example 8 were used, and the coating separator of Example 8 .

Example  9

Except that 118 g of distilled water and 113.8 g (6.8 g in terms of NV, 10 wt% with respect to the total weight of boehmite) of the binder prepared in Synthesis Example 9 were used, and the coating separator of Example 9 was used .

Example  10

(29.9 g, 3.4 g in terms of NV, 5% by weight based on the total weight of the boehmite) and 25% by weight of PVDF water dispersion (Solef 90000, manufactured by Solvay, 13.7 g, g, 5% by weight based on the total weight of the boehmite) was used in place of the coating separator of Comparative Example 1, to thereby obtain the coating separator of Example 10.

Example  11

(36.7 g, 3.4 g in terms of NV, 5 wt% based on the total weight of boehmite) and 25 wt% PVDF water dispersion (Solef 90000, manufactured by Solvay, 13.7 g, g, 5% by weight based on the total weight of the boehmite) was used in place of the coating separator of Comparative Example 1, to obtain the coating separator of Example 11.

Example  12

(29.9 g, 3.4 g in terms of NV, 5 wt% based on the total weight of the boehmite) and 16.9 wt% of a water-insoluble acrylic water dispersion (Hitachi Chemical Company, Ltd.) Manufactured by Seiko Epson Corporation, 20.2 g, 3.4 g in terms of NV, 5% by weight based on the total weight of boehmite) was used in place of the coating separator of Comparative Example 1.

Example  13

(36.7 g, 3.4 g in terms of NV, 5 wt% based on the total weight of the boehmite) and 16.9 wt% of a water-insoluble acrylic water dispersion (Hitachi Chemical Company, Ltd.) 20 g, calculated as NV in an amount of 3.4 g, and 5% by weight based on the total weight of the boehmite) was used in place of the coating separator of Comparative Example 1 to obtain a coating separator of Example 13.

Example  14

Except that 157 g of distilled water and 75.6 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 10 were used, and the coating separator of Example 14 .

Example  15

Except that 156 g of distilled water and 76.4 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 11 were used, and the coating separator of Example 15 .

Example  16

Except that 156 g of distilled water and 76.4 g (6.8 g in terms of NV) of the binder (10 wt% based on the total weight of boehmite) prepared in Synthesis Example 12 were used instead of the coating separator of Example 16, .

Example  17

Except that 157 g of distilled water and 75.6 g (6.8 g in terms of NV, 10 wt% based on the total weight of boehmite) of the binder prepared in Synthesis Example 13 were used, and the coating separator of Example 17 .

Example  18

Except that 157 g of distilled water and 75.6 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of the boehmite) prepared in Synthesis Example 14 were used, and the coating separator of Example 18 .

Example  19

Except that 157 g of distilled water and 75.6 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of the boehmite) prepared in Synthesis Example 15 were used, and the coating separator of Example 19 .

Example  20

Except that 156 g of distilled water and 76.4 g (6.8 g in terms of NV) of the binder (10% by weight based on the total weight of boehmite) prepared in Synthesis Example 16 were used, and the coating separator of Example 20 .

Example  21

Except that 157 g of distilled water and 75.6 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 17 were used, and the coating separator of Example 21 .

Example  22

155 g of distilled water and 77.3 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of the boehmite) prepared in Synthesis Example 18 were used in place of the binder used in Comparative Example 1. The coating separator of Example 22 .

Example  23

Except that 157 g of distilled water and 75.6 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 19 were used instead of the coating separator of Example 23, .

Example  24

Except that 157 g of distilled water and 75.6 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 20 were used, and the coating separator of Example 24 .

Example  25

155 g of distilled water, and 77.3 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 20 were used in place of the coating separator of Example 25, .

Example  26

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

Example  27

Except that 157 g of distilled water and 75.6 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 22 were used instead of the coating separator of Example 27, .

Example  28

Except that 156 g of distilled water and 76.4 g (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) of the binder prepared in Synthesis Example 20 were used instead of the coating separator of Example 28, .

Comparative Example  3

Except that 157 g of distilled water and 75.6 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 26 were used. The coating separator of Comparative Example 3 .

Comparative Example  4

Except that 159 g of distilled water and 73.1 g of the binder (6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) prepared in Synthesis Example 27 were used, and the coating separator of Comparative Example 4 .

<3. Coating layer adhesion evaluation >

An adhesive tape (Cellotape (registered trademark) No. 405 manufactured by Nichiban co., Ltd.) Having a width of 1.5 cm was attached to the coated separator fixed on the stainless steel plate.

Then, a peel test machine (SHIMAZU EZ-S manufactured by Shimadzu Corporation) was used to measure the peel strength at 180 deg. Peeling.

The results of the adhesion evaluation are shown in Table 1 below.

<4. Heat shrinkage  Evaluation>

As shown in Fig. 2, the coating separator was cut into TD * MD = 60 mm * 80 mm, and marks were made at intervals of 50 mm using a Nosig (vernier caliper) in the TD / MD directions.

The separator was sandwiched between aluminum foils folded once and allowed to stand in a thermostatic chamber at 130 캜 for 60 minutes.

After the separator was taken out, the interval of display of each of the TD / MD was read by Nogus (Vernier calipers), and the heat shrinkage ratio was calculated according to the following formula (1).

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

On the other hand, in the following expression (1), the interval after heating is the interval in the TD direction.

[Equation 1]

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

<4-1. Air permeability  Evaluation>

The air permeability was evaluated by measuring the permeation time of 100 cc of air at 567 g of inner cylinder weight (pressure) and 28.6 mm (6.45 square centimeter) of permeation surface of a Gurley type manufactured by TOYO SEIKI Co., Ltd.

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

bookbinder Coated Separator Peel strength (mN / mm) Shrinkage (%) Permeability
(sec / 100cc) PAANA 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: Solef 90000
= 5: 5 Example 10 160 1.5 101 Synthesis Example 2: solef90000
= 5: 5 Example 11 120 1.5 105 Synthesis Example 1: Synthesis of 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

Table 1 shows that the binders of Synthesis Examples 1 to 24, Synthesis Examples 26 to 27, and the binders of Synthesis Example 1 and Synthesis Example 2 were excellent in heat resistance and adhesive strength have.

It is also understood that these binders have low air permeability.

<5. Secondary Battery Manufacturing>

Example  29

(Preparation of negative electrode mixture slurry)

By mixing water with 96% by mass of artificial graphite, 2% by mass of acetylene black, 1% by mass of a styrene butadiene copolymer (SBR) binder and 1% by mass of carboxymethyl cellulose (CMC) To prepare a mixed slurry.

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

(Preparation of negative electrode)

Subsequently, the gap of the coater was adjusted so that the applied amount (surface density) of the mixture after drying was 9.55 mg / cm ² , and the negative electrode mixture slurry was uniformly applied to the copper foil did.

Subsequently, the negative electrode material mixture slurry was dried for 15 minutes in an air blower dryer set at 80 占 폚.

Subsequently, the negative electrode mixture after drying was pressed by a roll press machine so that the compound density became 1.65 g / cm ³ .

Subsequently, the negative electrode mixture was vacuum-dried at 150 占 폚 for 6 hours to prepare a sheet-like negative electrode comprising the negative electrode collector and the 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 .} 96 mass% of ₁₅ O ₂ , ₂ mass% of Ketjenblack and 2 mass% of polyvinylidene fluoride were dispersed in N-methyl-2-pyrrolidone to form a positive electrode mixture slurry.

On the other hand, the nonvolatile component in the positive electrode material mixture slurry was 50 mass% with respect to the total mass of the slurry.

(Preparation of anode)

Subsequently, the gap of the coater was adjusted so that the applied amount (surface density) of the mixture after drying was 22.7 mg / cm ² , and the positive electrode material mixture slurry was applied onto the current collecting foil as the current collector by this bar coater.

Subsequently, the positive electrode material mixture slurry was dried for 15 minutes in a blower dryer set at 80 캜.

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

Subsequently, the positive electrode mixture was vacuum-dried at 80 占 폚 for 6 hours to prepare a sheet-like positive electrode comprising a positive electrode collector and a positive electrode active material layer.

(Preparation of Lithium Ion Secondary Battery)

Cathode The anode shown in the production example of the anode was cut into a circle having a diameter of 1.55 cm and the anode shown in the production example of the cathode was cut into a circle having a diameter of 1.3 cm.

Then, the coated separator produced in Example 1 was cut into a circular shape having a diameter of 1.8 cm.

A positive electrode cut into a circle of 1.3 cm in diameter, a coating separator of Example 1 cut into a circle of 1.8 cm in diameter, a negative electrode cut into a circle of 1.55 cm in diameter, and a spacer as a spacer were prepared in a stainless steel coin outer container having a diameter of 2.0 cm A copper foil having a thickness of 200 占 퐉 and cut into a circle having a diameter of 1.5 cm was stacked in this order.

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

Then, a cap made of stainless steel was put on a container through a packing made of polypropylene, and the container was sealed with an adapter for making a coin cell.

Thus, a lithium ion secondary battery (coin cell) according to Example 14 was produced.

Example  30 to 56, Comparative Example  5 and 6

The lithium ion secondary batteries of Examples 30 to 56 and Comparative Examples 5 to 8 were fabricated in the same manner as in Example 29 except that the separators shown in Table 2 were used.

<6. Evaluation of cycle life>

The lithium ion secondary batteries according to each of the Examples and Comparative Examples were charged and discharged once at 25 ° C at 0.2C.

Thereafter, the charge / discharge cycle for charging / 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 cycle of 1.0C charge / discharge cycle) by the discharge capacity at 1 cycle (1.0C charge / discharge cycle first time).

The larger the capacity retention rate, the better the cycle life.

The evaluation results are collectively 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

It can be seen from Table 2 that the cycle characteristics of the lithium ion secondary battery according to the present embodiment are improved. It is also seen that the cycle characteristics are particularly improved when a water-insoluble resin is added as a binder.

On the other hand, the separator of Comparative Example 1 had a satisfactory peel strength and shrinkage ratio, but the secondary battery using the separator of Comparative Example 1 had lower cycle characteristics. This is considered to be due to the fact that the air permeability of Comparative Example 1 was high and moisture remained in the separator.

Therefore, it can be seen that even if an acrylic resin obtained by polymerizing only the carboxyl group-containing acrylic monomer (for example, sodium polyacrylate of Comparative Example 1) is used as the binder, the cycle characteristics can not be improved.

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

As described above, the binder according to the present embodiment has high heat resistance, strong adhesive force, and at the same time can improve cycle characteristics.

Therefore, by manufacturing the separator 40 using the binder according to the present embodiment and manufacturing the lithium ion secondary battery 10 using the separator 40, the cycle characteristics of the lithium ion secondary battery 10 can be improved.

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

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope 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 can also be used for other kinds of secondary batteries.

10 Lithium ion secondary battery
20 anode
21 anode collector
22 cathode active material layer
30 cathode
31 cathode collector
32 Anode active material layer
40 Separator
40a
40b coating layer

Claims (11)

A separator for a secondary battery comprising a substrate and a coating layer formed on at least one surface of the substrate,
Wherein the coating layer comprises a binder comprising an acrylic resin,
Wherein the binder containing the acrylic resin comprises a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer,
Wherein the mixing ratio of the carboxyl group-containing acrylic monomer and the acrylic acid derivative monomer is 20:80 to 80:20 in a molar ratio. The method according to claim 1,
Wherein 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. The method according to claim 1,
Wherein 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. The method of claim 3,
Wherein 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. The method according to claim 1,
Wherein the carboxyl group-containing acrylic monomer comprises an alkali metal salt or an ammonium salt. The method according to claim 1,
Wherein the coating layer further comprises a water-insoluble resin. The method according to claim 6,
Wherein the water-insoluble resin comprises polyvinylidene fluoride, a water-insoluble acrylic resin, or a combination thereof. The method according to claim 1,
Wherein the coating layer further comprises polyvinyl alcohol. The method according to claim 1,
Wherein the coating layer further comprises inorganic particles. 10. The method of claim 9,
Wherein the inorganic particles comprise 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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