KR20160079623A - Binder for rechargeable battery, separator for rechargeable battery inclduing same, and rechargeable battery including same - Google Patents

Abstract

Provided is a binder for a secondary battery, comprising an IPN-type acryl-based resin. The IPN-type acryl-based resin comprises: a hard segment having a glass transition temperature higher than or equal to 50°C and lower than or equal to 200°C; and a soft segment having the glass transition temperature having higher than or equal to -100°C and lower than or equal to 30°C. Provided in an embodiment of the present invention is the binder for a secondary battery, having high heat resistance and strong adhesion force.

Description

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

The present invention relates to a binder for a secondary battery, a separator for a secondary battery comprising the same, and a secondary battery comprising the same.

2. Description of the Related Art Recently, with the progress of miniaturization and weight reduction of various electronic apparatuses, secondary batteries used for power supply of these electronic apparatuses are required to have higher capacity, smaller size, and lighter weight.

Among them, lithium ion secondary batteries have advantages such as high voltage, long life, high energy density and so on, and researches on lithium ion secondary batteries are being actively conducted, and they are being produced and sold at the same time.

The characteristics of such a lithium secondary battery can be largely determined by the characteristics of electrodes, electrolytes, and other battery materials used.

Particularly, the separator of the lithium ion secondary battery affects the cycle characteristics of the lithium ion secondary battery. And a slurry containing inorganic particles and a binder is applied to a porous substrate using a separator. The separator is referred to as a coating separator because a coating layer containing inorganic particles and a binder is formed on the porous substrate.

The binder serves to bind the inorganic particles to the porous polyethylene film as a porous base material.

When such a separator is used to manufacture a lithium ion secondary battery, the cyclic characteristics of the lithium ion secondary battery can be improved by using the porous polyethylene (PE) and the ceramic particles (one kind of inorganic particles) and also between the ceramic particles and the ceramic particles And depends on the characteristics of the binder having the binding force.

Particularly, when ceramic particles having high heat resistance are used for the coating layer, 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.

Further, it is necessary that the binder firmly bonds 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 useful for a binder for a coating separator.

Specifically, a binder composition obtained by mixing a polyvinylidene fluoride (PVDF) 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 as a binder for a coating separator. However, PVDF binders must be used in excess in the separator in order to maintain a sufficient adhesive strength, and it is difficult to maintain a stable structure of the coating layer by the impregnation of the electrolyte and the mass transfer of lithium ions during charging and discharging of the lithium ion secondary battery.

As a method for solving such a problem, for example, there is a method of improving the adhesion force with an inorganic oxide (one kind of inorganic particles) by using a porous polyethylene, a binder containing a chemical structure with strong adhesion and a silane coupling agent, or A method of using a binder containing an IPN (interpenetrating polymer network) resin obtained by polymerizing a PVDF polymer and a hydrophilic polymer (unsaturated carboxylic acid) (see, for example, JP-A-2013-211273) is known.

However, the binder satisfies the adhesive force to either the porous polyethylene or the inorganic particle, but does not have a sufficient adhesive force to both the porous polyethylene and the inorganic particle.

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.

An embodiment of the present invention is to provide a binder for a secondary battery having high heat resistance and strong adhesive force.

Another embodiment of the present invention is to provide a separator for a secondary battery comprising the binder.

Another embodiment of the present invention provides a lithium secondary battery comprising the binder.

According to an embodiment of the present invention, there is provided a semiconductor device comprising: a hard segment having a glass transition temperature (Tg) of 50 DEG C or more and 200 DEG C or less; And an interpenetrating network (IPN) type acrylic resin including a soft segment having a glass transition temperature (Tg) of -100 DEG C to 30 DEG C.

In one embodiment of the present invention, the value of the Hildebrand solubility parameter of the hard segment may be greater than or equal to 21 and less than or equal to 25, and the value of the Hildebrand solubility parameter of the soft segment may be greater than or equal to 16 and less than or equal to 25.

The hard segment may comprise at least one selected from the group consisting of polymethacrylonitrile, poly N- (isobutoxymethyl) acrylamide and poly N-phenyl methacrylamide, wherein the soft segment is selected from the group consisting of polybutyl acrylate And poly-2-cyanoethyl acrylate.

According to another embodiment of the present invention, there is provided 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 the binder for the secondary battery.

The coating layer may further include inorganic particles.

According to another embodiment of the present invention, there is provided a secondary battery including the separator.

The binder according to one embodiment of the present invention includes an IPN type acrylic resin including a hard segment having a high glass transition temperature and a soft segment having a low glass transition temperature, and thus has high heat resistance and strong adhesion.

From the above, it can be seen that the binder according to the present embodiment has high heat resistance and strong adhesive force.

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

Hereinafter, the present invention will be described in more detail.

According to one embodiment of the present invention, there is provided a thermoplastic resin composition comprising a hard segment having a glass transition temperature (Tg) of not less than 50 DEG C and not more than 200 DEG C and a soft segment having a glass transition temperature (Tg) A binder for a secondary battery comprising an IPN (Interpenetrating network) type acrylic resin.

Such secondary battery binder has high heat resistance and strong adhesive force.

The value of the Hildebrand solubility parameter of the hard segment is greater than or equal to 21 and less than or equal to 25 and the value of the Hildebrand solubility parameter of the soft segment is greater than or equal to 16 and less than or equal to 25. The binder having such physical properties can have high heat resistance and strong adhesive force.

The hard segment may comprise at least one selected from the group consisting of polymethacrylonitrile, poly N- (isobutoxymethyl) acrylamide and poly N-phenyl methacrylamide, wherein the soft segment comprises polybutyl acrylate and Poly-2-cyanoethyl acrylate, and the like. The binder having such a constitution can have high heat resistance and strong adhesive force.

Another embodiment of the present invention provides 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 the binder for the secondary battery. That is, the separator according to one embodiment of the present invention has a coating layer on the surface of a substrate, and is a binder for forming the coating layer. The separator has a high glass transition temperature (Tg) hard segment and a low glass transition temperature (Tg) soft segment The heat resistance of the separator and the adhesion between the substrate and the coating layer, that is, the adhesion strength, can be improved by using a binder composition comprising an acrylic resin of the IPN (Interpenetrating network) structure.

The separator is manufactured using a binder for a secondary battery having high heat resistance and strong adhesive force.

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

The coating layer may further include inorganic particles. Since the coating layer further contains the inorganic particles, the secondary battery can be further improved in cycle characteristics by using the separator.

According to another embodiment of the present invention, there is provided a secondary battery including the separator. Such a secondary battery can exhibit improved cycle characteristics.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

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 lithium ion secondary battery according to a preferred embodiment of the present invention will be described in detail.

(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 an anode 20, a cathode 30, a separator 40, and a non-aqueous electrolyte.

Li / Li < + >) and 5.0 V or less, particularly 4.5 V or more and 5.0 V or less, for example, in the lithium ion secondary battery 10.

The shape of the lithium ion secondary battery 10 is not particularly limited. That is, the lithium ion secondary battery 10 may have any shape such as a cylindrical shape, a square shape, a laminate shape, a button shape, or 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 suitable conductor, and may include, for example, aluminum, stainless steel, and nickel coated steel.

The positive electrode active material layer 22 includes at least a positive electrode 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, 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, 0.15? 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 .

Examples of the conductive material include carbon black such as Ketjen black and acetylene black, natural graphite, artificial graphite and the like, but it is not particularly limited as long as it is for increasing the conductivity of the anode.

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

The positive electrode active material layer 22 can be produced, for example, in the following manner.

First, a positive electrode active material, a conductive material, and a binder are dry-mixed to prepare a positive electrode composite material.

The positive electrode material mixture slurry is dispersed in an appropriate organic solvent to prepare a positive electrode material slurry. The positive electrode material slurry is coated on the current collector 21, followed by drying and rolling to produce a positive electrode active material layer.

(Cathode 30)

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

The current collector 31 may be any conductor, and examples thereof include aluminum, stainless steel, and nickel-plated steel.

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.

The negative electrode active material includes, for example, 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 fine particles of these oxides and graphite active material , "Fine particles of silicon or tin", "alloy containing silicon or tin as a base material", and "titanium-based oxide such as Li ₄ Ti ₅ O ₁₂ ".

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

As the negative electrode active material, for example, metal lithium and the like can be mentioned.

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

The mass ratio of the negative 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 this embodiment.

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

First, a negative electrode active material and a binder are dry mixed to produce a negative electrode composite.

The negative electrode material mixture slurry is dispersed in an appropriate solvent to prepare a negative electrode material slurry. The negative electrode material mixture slurry is coated on the current collector 31, followed by drying and rolling to produce the negative electrode active material layer 32.

(Separator 40)

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

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

As the base material 40a, a porous film (porous film) or nonwoven fabric exhibiting excellent high rate discharge performance can be used singly or in combination.

As the resin constituting the substrate 40a, for example, polyolefin resins represented by polyethylene, polypropylene, etc., polyethylene terephthalate, polybutylene terephthalate ), Polyvinylidene fluoride, vinylidene fluoride (VDF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride- Vinylidene fluoride-tetrafluoroethylene copolymers, vinylidene fluoride-trifluoroethylene copolymers, vinylidene fluoride-fluoroethylene copolymers, vinylidene fluoride-hexa Fluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-ethylene copolymer, But are not limited to, fluoride-propylene copolymers, vinylidene fluoride-trifluoro propylene copolymers, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymers, vinylidene fluoride- Tetrafluoroethylene copolymer, and the like.

The coating layer 40b includes inorganic particles (filler) and a binder.

The inorganic particles include, for example, inorganic particles having high heat resistance.

Specific examples of such inorganic particles include oxides of silicon, aluminum, magnesium and titanium, and hydroxides thereof. Or boehmite as an inorganic particle.

Since the inorganic particles having such high heat resistance are included in the separator 40, the cycle characteristics of the lithium ion secondary battery 10 can be improved.

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

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

In one embodiment of the present invention, the binder includes an IPN type acrylic resin.

The IPN type acrylic resin may include a hard segment having a glass transition temperature (Tg) of 50 DEG C or higher and 150 DEG C or lower and a soft segment having a glass transition temperature (Tg) of -100 DEG C or higher and 30 DEG C or lower. The IPN type acrylic resin can be manufactured by IPNing the hard segment and the soft segment.

By using the IPN type acrylic resin including the hard segment having the high glass transition temperature (Tg) and the soft segment having the low glass transition temperature (Tg) as the binder for the coating layer 40b, the heat resistance of the separator 40 And adhesion between the base material 40a and the coating layer 40b can be improved.

In the embodiment of the present invention, since the coating layer 40b is formed by using the IPN type acrylic resin as a binder, the adhesion strength between the separator 40 and the electrodes (the anode 20 and the cathode 30) Can be improved.

As such, the safety and cycle life of the lithium ion secondary battery 10 can be improved as the adhesion strength is improved.

Whether or not the acrylic resin as the binder according to one embodiment of the present invention has or does not have the IPN structure can be determined by measuring the SEM image of the polymer microparticles of the hard segment and the polymer obtained by reacting the soft segment with the hard segment It can be confirmed by comparing the SEM images of the fine particles and judging whether or not the structures of the polymer fine particles observed from these SEM images are similar.

When the structure is similar, it means that the monomer of the soft segment reacted with the polymer fine particles of the hard segment is polymerized in the state of being absorbed by the polymer fine particles of the hard segment, that is, the IPN type polymer is formed.

Also, in one embodiment of the present invention, the glass transition temperature (Tg) is a glass transition temperature (Tg) when each hard segment and soft segment is a homopolymer, and the glass transition temperature Tg ) Is a value measured using a differential scanning calorimeter (DSC).

As the hard segment, it is appropriate to use a Hildebrand solubility parameter value (hereinafter referred to as " SP value ") of 21 or more and 25 or less.

By using a hard segment having an SP value of not less than 21 and not more than 25, it is possible to obtain an effect that excessive swelling of the electrolyte is hard to occur.

Examples of hard segments having such SP values include polymethacrylonitrile (SP value 23.7), poly N- (isobutoxymethyl) acrylamide (SP value 21.2), poly N-phenyl methacrylamide 22.4).

One of these hard segments may be used alone, or a plurality of hard segments may be used in combination.

As the soft segment, it is appropriate to use an SP value of 16 or more and 25 or less.

By setting the SP value of the soft segment to 16 or more and 25 or less, it is possible to prevent the compatibility with the hard segment from excessively deteriorating.

Examples of the soft segment having such an SP value include polybutyl acrylate (SP value: 17.5) and poly-2-cyanoethyl acrylate (SP value: 21.6).

One of these soft segments may be used alone, or a plurality of soft segments may be used in combination.

On the other hand, when the hard segment and the soft segment have an SP value within the above-mentioned range, the absolute value of the difference between the SP value of the hard segment and that of the soft segment becomes small, so that compatibility between the hard segment and the soft segment is improved.

Therefore, the obtained acrylic resin can easily form an IPN type structure.

The separator 40 can be manufactured, for example, in the following manner.

First, an inorganic particle dispersion 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.

As the solvent for the inorganic particle dispersion, a solvent such as a solvent for the binder solution may be suitably used.

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.

Subsequently, the inorganic particle dispersion and the binder solution are mixed to prepare a slurry.

The slurry may be optionally added with the same solvent as the solvent of the binder solution to adjust the concentration of the inorganic particles and the binder.

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 the coating layer 40b.

The substrate 40a may be immersed in the slurry.

According to this process, the separator 40 is manufactured.

1, the coating layer 40b is formed only on the surface of the base material 40a, but the coating layer 40b may be formed in the thin hole of the base material 40a.

As the non-aqueous electrolyte, any non-aqueous electrolyte used conventionally for lithium secondary batteries can be used without limitation.

The non-aqueous electrolyte has 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 are not limited thereto.

LiFF ₆ , LiPF _6-x (C _n F _{2n + 1} ) x (where 1 <x <6, n = 1 or 2) is used as the electrolyte salt, for example, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , , 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-benzoate, (C ₂ H ₅ ) ₄ N-phthalate, stearyl sulfonic acid lithium, octyl sulfonic acid, dodecyl benzene sulphonic acid and the like And the like. These ionic compounds may be used singly or in combination of two or more.

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

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

Various additives may be added to the nonaqueous electrolyte solution.

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)

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

The anode 20 can be manufactured by the following process.

First, a slurry is prepared by mixing a cathode active material, a conductive material and a binder, and dispersing the mixture in a solvent (for example, N-methyl-2-pyrrolidone).

The slurry is developed (for example, applied) onto the current collector 21 and dried to prepare the positive electrode active material layer 22.

In this case, the coating method is not particularly limited, and examples of the coating method include a knife coater method and a gravure coater method.

Hereinafter, each coating step may be carried out in the same manner.

Subsequently, the positive electrode active material layer 22 is pressed using a press machine to produce the positive electrode 20. Then,

The cathode 30 may also be manufactured in the same manner as the anode 20.

First, a slurry is prepared by dispersing a mixture of an anode active material and a binder in a solvent (for example, N-methyl-2-pyrrolidone, water).

The slurry is developed (for example, coated) on the current collector 31 and dried to produce the negative electrode active material layer 32.

Subsequently, the negative electrode active material layer 32 is pressed by using a press machine to produce the negative electrode 30.

The separator 40 can be manufactured, for example, by the following method.

First, an inorganic particle dispersion and a binder solution are prepared. Subsequently, the inorganic particle dispersion and the binder solution are mixed to prepare a slurry.

The slurry may optionally be added with the same solvent as the solvent of the binder solution to adjust the concentration of the inorganic particles and the binder.

Then, the slurry is developed (for example, coated) on the substrate 40a and dried to prepare a coating layer 40b.

At this time, the base material 40a may be immersed in the slurry.

The separator 40 is manufactured by this process.

Subsequently, the separator 40 is placed between the anode 20 and the cathode 30 to prepare an electrode structure.

Then, the produced electrode structure is processed into a desired shape (for example, a cylindrical shape, a square shape, a laminate shape, a button shape, or the like), and inserted into the container of the above-described shape.

Subsequently, an electrolyte solution having the above composition is injected into the container, and the electrolyte solution is impregnated into each pore in the separator. This process produces a lithium ion secondary battery.

When the lithium ion secondary battery 10 is manufactured using the separator 40 manufactured using the binder according to one embodiment of the present invention, the cycle characteristics of the lithium ion secondary battery 10 can be improved.

Further, since the heat shrinkage of the separator 10 is also suppressed, thermal runaway of the lithium ion secondary battery 10 can be suppressed, and as a result, the safety of the lithium ion secondary battery 10 can be improved.

Hereinafter, examples and comparative examples of the present invention will be described. The following embodiments are only examples of the present invention, and the present invention is not limited to the following embodiments.

<1. Binder resin synthesis >

[Synthesis Example 1: synthesis of polymethacrylonitrile (PMAN) fine particle solution (hard segment (Tg of homopolymer: 67 ° C)]]

600 g of distilled water was added to a four-neck separable flask of 1000 ml equipped with a stirrer, a thermometer and a cooling tube, and the pressure was reduced to 10 mmHg with a diaphragm pump and the internal pressure was returned to normal pressure with nitrogen.

Then, sodium dodecyl sulfate (7.5 g, 0.026 mol) was dissolved in 20 g of deaerated distilled water and added. Methacrylonitrile (150 g, 2.236 mol) and ammonium persulfate (2.55 g, 0.0112 mol, 0.005 equivalent) After the addition, the mixture was stirred at 600 rpm.

The reaction was carried out for 6 hours while controlling the heating so that the temperature of the reaction solution stably remained between 70 캜 and 80 캜.

After the reaction product was cooled to room temperature, 2 ml of the reaction solution was taken and the nonvolatile component (NV) was measured. As a result, 20.0% (theoretical value 21%) was obtained.

Synthesis Example 2: Synthesis of poly (N- (isobutoxymethyl) acrylamide (PIBMAAM) fine particle solution (hard segment (Tg of homopolymer: 135 deg.

600 g of distilled water was added to a four-neck separable flask of 1000 ml equipped with a stirrer, a thermometer and a cooling tube, and the pressure was reduced to 10 mmHg with a diaphragm pump and the internal pressure was returned to normal pressure with nitrogen.

Then, sodium dodecylsulfate (7.5 g, 0.026 mol) was dissolved in 20 g of deaerated distilled water and added to the mixture. Then, N- (isobutoxymethyl) acrylamide (150 g, 1.048 mol) and ammonium persulfate mol, 0.005 eq.) was added thereto, followed by stirring at 600 rpm.

The reaction was allowed to proceed for 6 hours while the heating was controlled so that the temperature of the reaction solution was stably maintained between 70 캜 and 80 캜.

After the reaction product was cooled to room temperature, 150 g of water was distilled off using a rotary evaporator, and diluted with distilled water so that the nonvolatile component (NV) became 20.0%.

Synthesis Example 3: Synthesis of poly N- (isobutoxymethyl) acrylamide (PIBMAAM) fine particle solution (hard segment (Tg of homopolymer: 165 ° C)

600 g of distilled water was added to a four-neck separable flask of 1000 ml equipped with a stirrer, a thermometer and a cooling tube, and the pressure was reduced to 10 mmHg with a diaphragm pump and the internal pressure was returned to normal pressure with nitrogen.

Then, sodium dodecyl sulfate (7.5 g, 0.026 mol) was dissolved in 20 g of deaerated distilled water, and then methacrylonitrile (150 g, 0.931 mol), ammonium persulfate (0.935 g, 0.00465 mol, And the mixture was stirred at 600 rpm.

The reaction was allowed to proceed for 6 hours while the heating was controlled so that the temperature of the reaction solution was stably maintained between 70 캜 and 80 캜.

After the reaction product was cooled to room temperature, 150 g of water was distilled off using a rotary evaporator, and diluted with distilled water so that the nonvolatile component (NV) became 20.0%.

<2. Synthesis of binder >

(Example 1: synthesis of polymethacrylonitrile (PMAN) -polybutyl acrylate (PBu) IPN polymer (PMAN: PBu = 60: 40)

100 g of the polymethacrylonitrile fine particle solution (hard segment, NV 20.0%, 20 g in terms of the weight of the resin component) synthesized in Synthesis Example 1, 100 g of distilled water (100 g) in a 1000 ml four-neck separable flask equipped with a stirrer, a thermometer and a cooling tube , The pressure was reduced to 25 mmHg with a diaphragm pump, and the operation of returning the internal pressure to normal pressure with nitrogen was repeated five times.

Butyl acrylate (soft segment (Tg of homopolymer: -55 ° C), 13.5 g, 0.105 mol) was added, and the mixture was stirred at 60 ° C for 2 hours.

Then, azoisobutyronitrile (AIBN, 0.120 g, 0.53 mmol, 0.005 eq.) Was added, and the reaction was allowed to proceed for 6 hours while controlling the heating so as to keep the reaction temperature stable between 70 캜 and 80 캜.

After the reaction product was cooled to room temperature, it was diluted with distilled water so that the nonvolatile component (NV) became 15.0%.

(Example 2: synthesis of polymethacrylonitrile (PMAN) -polybutyl acrylate (PBu) IPN polymer (PMAN: PBu = 70: 30)

Except that 43.5 g of distilled water, butyl acrylate (8.6 g, 0.067 mol) and AIBN (0.077 g, 0.34 mmol, 0.005 equivalent) were used.

(Example 3: synthesis of polymethacrylonitrile (PMAN) -polybutyl acrylate (PBu) IPN polymer (PMAN: PBu = 80: 20)

Except that 25.5 g of distilled water, butyl acrylate (5.0 g, 0.039 mol) and AIBN (0.044 g, 0.20 mmol, 0.005 equivalent) were used.

Example 4: Synthesis of polymethacrylonitrile (PMAN) -poly 2-cyanoethyl acrylate (PCEA) IPN polymer (PMAN: PCEA = 60: 40)

100 g of the polymethacrylonitrile fine particle solution (hard segment, NV 20.0%, 20 g in terms of the weight of the resin component) synthesized in Synthesis Example 1, 100 g of distilled water (100 g) in a 1000 ml four-neck separable flask equipped with a stirrer, a thermometer and a cooling tube , The pressure was reduced to 25 mmHg with a diaphragm pump, and the operation of returning the internal pressure to normal pressure with nitrogen was repeated five times.

2-cyanoethyl acrylate (soft segment (Tg of the homopolymer: 4 DEG C), 13.5 g, 0.095 mol) was added, and the mixture was stirred at 60 DEG C for 2 hours.

Then, azoisobutyronitrile (AIBN, 0.108 g, 0.47 mmol, 0.005 eq.) Was added, and the reaction was allowed to proceed for 6 hours while the heating was controlled stably at a reaction temperature of 70 to 80 캜.

After the reaction product was cooled to room temperature, it was diluted with distilled water so that the nonvolatile component (NV) became 15.0%.

(Example 5: synthesis of polymethacrylonitrile (PMAN) -poly 2-cyanoethyl acrylate (PCEA) IPN polymer (PMAN: PCEA = 70: 30)

Except that 25.5 g of distilled water, 2-cyanoethyl acrylate (8.6 g, 0.060 mol) and AIBN (0.069 g, 0.30 mmol, 0.005 equivalent) were used.

Example 6: Synthesis of polymethacrylonitrile (PMAN) -poly 2-cyanoethyl acrylate (PCEA) IPN polymer (PMAN: PCEA = 70: 30)

Except that 25.5 g of distilled water, 2-cyanoethyl acrylate (5.0 g, 0.035 mol) and AIBN (0.040 g, 0.18 mmol, 0.005 equivalent) were used.

Example 7: Synthesis of poly N- (isobutoxymethyl) acrylamide (PIBMAAM) -poly 2-cyanoethyl acrylate (PCEA) IPN polymer (PIBMAAM: PCEA = 60:40)

In a 1000 ml four-neck separable flask equipped with a stirrer, a thermometer and a cooling tube, a solution of poly N- (isobutoxymethyl) acrylamide fine particles synthesized in Synthesis Example 2 (hard segment, NV 20.0% 20 g) and 67.5 g of distilled water were added. The internal pressure was reduced to 25 mmHg with a diaphragm pump, and the operation of returning the internal pressure to normal pressure with nitrogen was repeated five times.

2-cyanoethyl acrylate (soft segment (Tg of the homopolymer: 4 DEG C), 13.5 g, 0.095 mol) was added, and the mixture was stirred at 60 DEG C for 2 hours.

Then, azoisobutyronitrile (AIBN, 0.108 g, 0.47 mmol, 0.005 eq.) Was added and reacted for 6 hours while controlling the heating to keep the reaction temperature stable between 70 캜 and 80 캜.

After the reaction product was cooled to room temperature, it was diluted with distilled water so that the nonvolatile component (NV) became 15.0%.

Example 8: Synthesis of poly N- (isobutoxymethyl) acrylamide (PIBMAAM) -poly 2-cyanoethyl acrylate (PCEA) IPN polymer (PIBMAAM: PCEA = 70: 30)

Except that 25.5 g of distilled water, 2-cyanoethyl acrylate (8.6 g, 0.060 mol) and AIBN (0.069 g, 0.30 mmol, 0.005 equivalent) were used.

Example 9: Synthesis of poly N- (isobutoxymethyl) acrylamide (PIBMAAM) -poly 2-cyanoethyl acrylate (PCEA) IPN polymer (PIBMAAM: PCEA = 80:20)

Except that 25.5 g of distilled water, 2-cyanoethyl acrylate (5.0 g, 0.035 mol) and AIBN (0.040 g, 0.18 mmol, 0.005 equivalent) were used.

Example 10: Synthesis of poly N-phenylmethacrylamide (PPMAAM) -poly 2-cyanoethyl acrylate (PCEA) IPN polymer (PIBMAAM: PCEA = 60:40)

In a 1000 ml four-neck separable flask equipped with a stirrer, a thermometer and a cooling tube, 100 g of a poly-N-phenylmethacrylamide fine particle solution (hard segment, NV 20.0%, weight ratio of resin content 20 g) synthesized in Synthesis Example 3 , 67.5 g of distilled water was added, the pressure was reduced to 25 mmHg with a diaphragm pump, and the internal pressure was returned to normal pressure with nitrogen was repeated five times.

2-cyanoethyl acrylate (soft segment (Tg of the homopolymer: 4 DEG C), 13.5 g, 0.095 mol) was added, and the mixture was stirred at 60 DEG C for 2 hours.

Then, azoisobutyronitrile (AIBN, 0.108 g, 0.47 mmol, 0.005 eq.) Was added and reacted for 6 hours while controlling the heating to keep the reaction temperature stable between 70 캜 and 80 캜.

After the reaction product was cooled to room temperature, it was diluted with distilled water so that the nonvolatile component (NV) became 15.0%.

Example 11: Synthesis of poly N-phenylmethacrylamide (PPMAAM) -poly 2-cyanoethyl acrylate (PCEA) IPN polymer (PIBMAAM: PCEA = 70: 30)

Except that 25.5 g of distilled water, 2-cyanoethyl acrylate (8.6 g, 0.060 mol) and AIBN (0.069 g, 0.30 mmol, 0.005 equivalent) were used.

Example 12: Synthesis of poly N-phenylmethacrylamide (PPMAAM) -poly 2-cyanoethyl acrylate (PCEA) IPN polymer (PIBMAAM: PCEA = 80: 20)

Except that 25.5 g of distilled water, 2-cyanoethyl acrylate (5.0 g, 0.035 mol) and AIBN (0.040 g, 0.18 mmol, 0.005 equivalent) were used.

<3. Manufacture of coating separator>

(Example 13)

, 61.4 g of boehmite C20 (manufactured by TAIMEI CHEMICALS CO., LTD.) And 6.8 g of boehmite ACTILOX-200SM (manufactured by Nabalek Co.), 185 g of distilled water, and 45.3 g of binder 45.3 (zirconia beads, 0.5φ, loading rate: 60%, 2000 rpm, 10% by weight based on the total weight of boehmite) was added to the mixture, 4 times) to prepare a boehmite / binder mixed solution.

Thereafter, a gravure coater manufactured so that the coating amount after drying (loading amount) was 3.0 g / m ² was used, and a 12 μm thick polyethylene microporous membrane (T12-507, manufactured by SK Innovation) The solution was applied and dried to prepare a coating separator.

(Example 14)

A coating separator was produced in the same manner as in Example 13 except that the binder prepared in Example 2 was used.

(Example 15)

A coating separator was prepared in the same manner as in Example 13 except that the binder prepared in Example 3 was used.

(Example 16)

A coating separator was prepared in the same manner as in Example 13 except that the binder prepared in Example 4 was used.

(Example 17)

A coating separator was prepared in the same manner as in Example 13 except that the binder prepared in Example 5 was used.

(Example 18)

A coating separator was prepared in the same manner as in Example 13 except that the binder prepared in Example 6 was used.

(Example 19)

A coating separator was produced in the same manner as in Example 13 except that the binder prepared in Example 7 was used.

(Example 20)

A coating separator was produced in the same manner as in Example 13 except that the binder prepared in Example 8 was used.

(Example 21)

A coating separator was produced in the same manner as in Example 13 except that the binder prepared in Example 9 was used.

(Example 22)

A coating separator was produced in the same manner as in Example 13 except that the binder prepared in Example 10 was used.

(Example 23)

A coating separator was prepared in the same manner as in Example 13 except that the binder prepared in Example 11 was used.

(Example 24)

A coating separator was prepared in the same manner as in Example 13 except that the binder prepared in Example 12 was used.

(Comparative Example 1)

Except that 25% by weight of polyvinylidene fluoride aqueous dispersion (Solef90000 manufactured by Solvay Co., Ltd.) (27.2 g, 6.8 g in terms of NV, 10% by weight based on the total weight of boehmite) was used as a binder To prepare a coating separator.

<4. Coating layer adhesion evaluation >

Adhesive tape (Celotape (registered trademark) No. 405 made by Nichiban Co., ltd.) Having a width of 1.5 cm was attached to the coated separator fixed on the stainless steel plate.

The peel strength was measured by a peel test machine (SHIMAZU EZ-S manufactured by Shimadzu Corporation) using a 180 ㅀ peeling test.

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

<5. Heat Shrinkage Evaluation>

As shown in Fig. 2, the coated separator was cut into TD * MD = 60 mm * 80 mm, and the distance was indicated at intervals of 50 mm by using a nonius in the TD / MD direction.

The separator was sandwiched between two folded aluminum foils, and kept in a thermostat at 130 캜 for 60 minutes. Subsequently, after the separator was taken out, the display interval of each of the TD / MD was read by Nogus and the heat shrinkage rate was calculated according to the following formula.

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

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

bookbinder Coated Separator Peel strength (mN / mm) Shrinkage (%) Example 1 Example 13 30 1.5 Example 2 Example 14 29 2 Example 3 Example 15 28 2 Example 4 Example 16 29 1.5 Example 5 Example 17 27 2 Example 6 Example 18 26 2 Example 7 Example 19 27 2 Example 8 Example 20 28 2 Example 9 Example 21 27 1.5 Example 10 Example 22 28 1.5 Example 11 Example 23 29 2 Example 12 Example 24 29 2 PVDF Comparative Example 1 5 3

From the results shown in the above Table 1, it can be seen that the binder prepared according to Examples 1 to 12, that is, the hard segment having a Tg of 50 ° C or higher and 200 ° C or lower, and the soft segment having Tg of -100 ° C or higher and 30 ° C or lower, Type acrylic resin is superior to the PVDF binder in terms of heat resistance and adhesion.

<6. Secondary Battery Manufacturing>

(Example 25)

(Preparation of negative electrode slurry)

Water was added to the mixture to adjust the viscosity to 96% by weight of artificial graphite, 2% by weight of acetylene black, 1% by weight of a styrene butadiene copolymer (SBR) binder and 1% by weight of carboxymethyl cellulose (CMC) To prepare a slurry.

The nonvolatile component in the negative electrode slurry was 48% by weight based on the total weight of the slurry.

(Preparation of negative electrode)

Subsequently, the gap of the bar coater was adjusted so that the coating amount (area density) after drying was 9.55 mg / cm ² , and the negative electrode slurry was uniformly coated on the copper foil (collector, thickness 10 μm) using the bar coater .

Subsequently, the negative electrode slurry was dried for 15 minutes in a blower dryer set at 80 占 폚. The negative electrode mixture after drying was pressed using a roll press machine to have a compound density of 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 including the negative electrode collector and the negative electrode active material layer.

(Preparation of positive electrode slurry)

Solid solution oxides Li _1.20 Mn _0.55 Co _0.10 Ni _0.15 O ₂ 96 wt%, Ketjenblack 2 wt%, and polyvinylidene fluoride 2 wt% were dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode slurry.

On the other hand, the nonvolatile component in the positive electrode composite slurry was 50% by weight based on the total mass of the slurry.

(Preparation of positive electrode)

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

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

Subsequently, the dried positive electrode mixture was pressed by a roll press so that the compound density became 3.9 g / cm &lt; ^{3 &} gt ;.

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

(Production of lithium ion secondary battery)

The negative electrode prepared in the above process was cut into a circle having a diameter of 1.55 cm and the positive electrode prepared by the above process into a circle having a diameter of 1.3 cm.

Then, the coated separator produced according to Example 13 was cut into a circle 1.8 cm in diameter.

In a stainless steel coin type external container having a diameter of 2.0 cm, a positive electrode cut into a circle of 1.3 cm in diameter, a coating separator cut into a circle 1.8 cm in diameter, a negative electrode cut into a circle of 1.55 cm in diameter, and a circle 1.5 cm in diameter And a copper foil having a thickness of 200 mu m cut out in this order were laminated in this order.

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

Then, the polypropylene packing was sandwiched therebetween, and the stainless steel cap was covered with the container, and the container was sealed with an adapter for producing a coin cell.

In this process, a lithium ion secondary cell (coin cell) using the separator of Example 13 was produced.

(Examples 26 to 36 and Comparative Example 2)

Lithium ion secondary batteries of Examples 26 to 36 and Comparative Example 2 were produced in the same manner as in Example 25 except that the separators shown in Table 2 were used.

<7. Evaluation of cycle life>

The lithium ion secondary batteries according to Examples 25 to 36 and Comparative Example 2 were charged and discharged once at 25 ° C at 0.2C.

Thereafter, a 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 the time of 100 cycles (100th cycle of the 1.0C charge / discharge cycle) by the discharge capacity at the time of one cycle (first cycle of 1.0C charge / discharge cycle). The larger the capacity retention rate, the better the cycle life.

The results are shown in Table 2 below.

Coin cell Separator Capacity retention rate (%) after 100 cycles Example 25 Example 13 90 Example 26 Example 14 87 Example 27 Example 15 89 Example 28 Example 16 88 Example 29 Example 17 90 Example 30 Example 18 89 Example 31 Example 19 90 Example 32 Example 20 89 Example 33 Example 21 91 Example 34 Example 22 91 Example 35 Example 23 92 Example 36 Example 24 93 Comparative Example 2 Comparative Example 1 85

As shown in Table 2, it can be seen that the cycle characteristics of the lithium ion secondary batteries of Examples 25 to 36 were improved as compared with Comparative Example 2.

From these results, it can be seen that the binders of Examples 1 to 12 have high heat resistance and strong adhesive force.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples.

It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the technical idea defined in the appended claims. Quot; range &quot;

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.

[Description of Symbols]

10: Lithium ion secondary battery

20: anode

30: cathode

40: Separator

40a:

40b: Coating layer

Claims (7)

A hard segment having a glass transition temperature (Tg) of 50 DEG C or more and 200 DEG C or less; And an interpenetrating polymer network (IPN) type acrylic resin including a soft segment having a glass transition temperature (Tg) of -100 DEG C to 30 DEG C
Binder for secondary battery. The method according to claim 1,
Wherein the value of the Hildebrand solubility parameter of the hard segment is 21 or more and 25 or less and the value of the Hildebrand solubility parameter of the soft segment is 16 or more and 25 or less. The method according to claim 1,
Wherein the hard segment comprises at least one selected from the group consisting of polymethacrylonitrile, poly N- (isobutoxymethyl) acrylamide and poly N-phenyl methacrylamide, the soft segment comprising polybutyl acrylate and poly - &lt; / RTI &gt; cyanoethyl acrylate. And a coating layer formed on at least one surface of the substrate,
Wherein the coating layer comprises the binder for a secondary battery according to any one of claims 1 to 3
Separator for secondary battery. 5. The method of claim 4,
Wherein the coating layer further comprises inorganic particles. And a coating layer formed on at least one surface of the substrate, wherein the coating layer comprises a separator comprising the binder according to any one of claims 1 to 3
Containing secondary batteries. The method according to claim 6,
Wherein the coating layer further comprises inorganic particles.

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