KR20150059621A - Composition for coating separator, separator formed by using the composition, and battery using the separator - Google Patents

Abstract

The present invention relates to a separator, a composition for coating the separator, and an electrochemical battery including the separator which comprise: a polyolefin-based base material film; and a coating layer formed on one side or both sides of the base material film comprising an organic binder and an inorganic particle. The organic binder comprises an acrylic copolymer including a repeating unit derived from a methacrylate monomer and a repeating unit derived from a monomer containing an acetate group.

Description

TECHNICAL FIELD The present invention relates to a separator coating composition, a separator formed of the coating composition, and a battery using the separator, and a battery using the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

Disclosed is a coating separator wherein shrinkage in a battery is prevented, and heat resistance and shape stability are improved.

A separator for an electrochemical cell means an interlayer that keeps the ion conductivity constant while isolating the positive electrode and the negative electrode from each other in the battery to enable charging and discharging of the battery.

Recently, as the stability of the battery has come to the fore, the role of the separator to prevent short-circuiting between the positive and negative electrodes has been dealt with. Generally used polyolefin-based fabrics have high heat shrinkage at high temperature and low physical durability. Therefore, if an abnormality occurs in the battery and the internal temperature rises, the separation membrane may easily deform, and if it is serious, an explosion may occur. Therefore, improvement of heat resistance and shrinkage resistance associated with high temperature stability is an important factor in development of a separator. A non-woven fabric separator which is manufactured by processing a heat-resistant polymer in the form of a fiber, a ceramic separator which is formed by connecting inorganic particles using a small amount of binder, a coating separator for coating a ceramic and a binder on a conventional polyolefin or non- (Korean Patent No. 10-0775310) and the like are being developed. In recent years, due to limitations on the thickness of the coating layer due to the restriction of the thickness of the separator, studies are being conducted to secure physical properties through a thinner coating layer.

Korean Patent No. 10-0775310

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Disclosed is a coating separator wherein shrinkage in a battery is prevented, and heat resistance and shape stability are improved.

According to an embodiment of the present invention, there is provided an organic binder comprising: an acrylic copolymer comprising a repeating unit derived from a (meth) acrylate monomer and a repeating unit derived from an acetate group-containing monomer; Inorganic particles; And a solvent are provided.

According to another embodiment of the present invention, there is provided a polyolefin-based substrate film, and a coating layer formed on one or both surfaces of the base film, the organic binder including inorganic particles, wherein the organic binder includes a repeating unit derived from a (meth) And an acrylic copolymer containing a repeating unit derived from a monomer containing an acetate group.

According to another example of the present invention, a separator comprising a polyolefin-based substrate film and a coating layer formed on one surface or both surfaces of the substrate film and including an organic binder and inorganic particles is placed between an anode and a cathode, 10 seconds 20kgf / cm ² to 100kgf / cm ² when the pressure after compression as the left at 130 ℃ 10 bungan crimp shrinkage of not more than 10% of the membrane, respectively MD and TD directions is provided.

According to another embodiment of the present invention, there is provided an electrochemical cell, particularly a lithium secondary battery, including a separator according to one example.

The separation membrane according to the present invention has an effect of preventing shrinkage in the battery and improving heat resistance. Further, the separation membrane according to the present invention is further excellent in properties such as air permeability and mechanical strength.

Hereinafter, the present invention will be described in more detail. Those skilled in the art will appreciate that those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

A separation membrane according to an embodiment of the present invention includes a base film and a coating layer formed on one or both sides of the base film.

The base film may be polyolefin-based. The polyolefin based film has excellent shut down function and can contribute to improvement of the safety of the battery. The polyolefin based film may be selected from the group consisting of a polyethylene single film, a polypropylene single film, a polyethylene / polypropylene double film, a polypropylene / polyethylene / polypropylene triple film and a polyethylene / polypropylene / polyethylene triple film . The thickness of the polyolefin-based film may be 1 to 40 탆, and specifically 5 to 15 탆. When a base film within the above-mentioned thickness range is used, it is possible to produce a separator having an appropriate thickness which is thick enough to prevent a short circuit between the positive and negative electrodes of the battery, but not thick enough to increase the internal resistance of the battery.

The coating layer may be formed of a coating composition, and the coating composition may include an organic binder, inorganic particles, and a solvent.

Specifically, the organic binder may be an acrylic copolymer, for example, an acrylic copolymer containing a repeating unit derived from a (meth) acrylate monomer and a repeating unit derived from an acetate group containing monomer. Use of an acrylic copolymer having a repeating unit derived from a (meth) acrylate monomer as a binder and a repeating unit derived from an acetate group-containing monomer prevents shrinkage of the separator and improves heat resistance in a cell where the separator is actually used have. Generally, the heat resistance of the separation membrane is measured by applying heat to the separation membrane itself under a certain condition and measuring the heat resistance of the separation membrane in the longitudinal direction of the separation membrane (hereinafter referred to as "MD direction") and in the width direction Shrinkage. However, when the separator is disposed between the electrodes in the cell and the heat resistance and the shrinkage ratio in the compressed state are evaluated, the actual shape stability of the separator in the cell can be better reflected. (Meth) acrylate-based monomer and a repeating unit derived from an acetate group as a binder, the acrylic copolymer improves the adhesion between the electrode and the separator, and the adhesion of the acrylic copolymer improves the heat resistance And to prevent shrinkage of the separator. That is, the shape stability of the separator in the battery is improved and the safety of the battery is improved accordingly.

The glass transition temperature (Tg) of the acrylic copolymer may be less than 100 ° C, for example, 20 to 60 ° C. Within this range, good adhesion can be obtained at a temperature at which the separator is sandwiched between the electrodes, thereby improving the shrinkage rate and improving the heat resistance.

The acrylic copolymer having the repeating unit derived from a (meth) acrylate monomer and the repeating unit derived from an acetate group-containing monomer is not particularly limited as long as it can form a good adhesive force at a temperature at which it is compressed between the positive electrode and the negative electrode, For example, the acrylic copolymer may be at least one selected from the group consisting of butyl (meth) acrylate, propyl (meth) acrylate, ethyl (meth) acrylate and methyl (meth) May be a copolymer produced by polymerizing monomers and at least one acetate group-containing monomer selected from the group consisting of vinyl acetate and allyl acetate.

The repeating unit derived from an acetate group-containing monomer may be a repeating unit represented by the following formula (1)

 [Chemical Formula 1]

In Formula 1,

R < _{1 >} is a single bond, a straight chain or branched alkyl of 1 to 6 carbon atoms, R < ₂ > is hydrogen or methyl and l is an integer of 1 to 100,

The acrylic copolymer is prepared by copolymerizing the (meth) acrylate monomer and the acetate group-containing monomer such as vinyl acetate and / or allylacetate in a molar ratio of 3: 7 to 7: 3, specifically 4: 6 to 6: 4 , More specifically in a ratio of about 5: 5. The acrylic copolymer is obtained by copolymerizing, for example, butyl (meth) acrylate monomer, methyl (meth) acrylate monomer, and vinyl acetate and / or allyl acetate monomer in a weight ratio of 3 to 5: 0.5 to 1.5: 4 to 6 In a ratio of 4: 1: 5.

The inorganic particles are not particularly limited and inorganic particles that are conventionally used in the art can be used. Non-limiting examples of the inorganic particles usable in this embodiment include Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ , Ga ₂ O ₃ , TiO ₂ or SnO ₂ . These may be used alone or in combination of two or more. As the inorganic particles used in the present invention, for example, Al ₂ O ₃ (alumina) can be used.

The size of the inorganic particles used in this embodiment is not particularly limited, but may be an average particle diameter of 1 nm to 2,000 nm, for example, 100 to 1,000 nm, and 300 nm to 500 nm. In the case of using the inorganic particles having the above-mentioned size range, it is possible to prevent degradation of the dispersibility of the inorganic particles and the processability of the coating in the coating liquid, and the thickness of the coating layer can be appropriately controlled to prevent deterioration of mechanical properties and increase in electrical resistance . In addition, the size of the pores generated in the separation membrane is appropriately controlled, thereby reducing the probability of an internal short circuit occurring during charging and discharging of the battery.

In the preparation of the coating composition, the inorganic particles may be used in the form of an inorganic dispersion in which the inorganic particles are dispersed in an appropriate solvent. The suitable solvent is not particularly limited, and solvents commonly used in the art may be used. As an appropriate solvent for dispersing the inorganic particles, for example, acetone may be used. The inorganic dispersion may be prepared by a conventional method without any particular limitation. For example, Al ₂ O ₃ may be added in an appropriate amount to acetone, milled using a beads mill, A dispersion can be prepared.

In the coating layer, the inorganic particles may be contained in an amount of 70 to 99% by weight, specifically 75 to 95% by weight, more specifically 80 to 90% by weight, based on the total weight of the coating layer. When the inorganic particles are contained within the above range, the heat radiation characteristics of the inorganic particles can be sufficiently exhibited, and when the separator is coated using the inorganic particles, the heat shrinkage of the separator can be effectively suppressed.

Nonlimiting examples of the solvent usable in this embodiment include dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), dimethyl acetamide (DMAc), dimethyl carbonate DMC) or N-methyl pyrrolydone (NMP). The content of solvent based on the weight of the coating composition may be 20 to 99 wt%, specifically 50 to 95 wt%, and more specifically 70 to 95 wt%. When the solvent is contained in the above range, the coating agent is easily prepared and the drying process of the coating layer can be performed smoothly.

Hereinafter, a separation membrane and coating composition according to another embodiment of the present invention will be described. The coating layer and the coating composition according to this embodiment are distinguished from the above-mentioned embodiments in that a binder other than the acrylic copolymer is added. By further containing another binder in addition to the acrylic copolymer, adhesive strength and heat resistance can be further improved. Hereinafter, other binders added will be mainly described.

Examples of the binder added in addition to the acrylic copolymer include polyvinylidene fluoride (PVdF) homopolymer, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polymethyl (PMMA), polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), polyvinylacetate (PVAc), polyethylene oxide (PEO), cellulosic acetate cellulose acetate (CA), cellulose acetate butyrate (CAB), cellulose acetate propionate (CAP), cyanoethylpullulan (CYEPL), and cyanoethylpolyvinyl alcohol cyanoethylpolyvinylalcohol (CR-V), cyanoethylcellulose (CEC), and cyanoethylcellulose But are not limited to, those selected from the group consisting of cyanoethylsucrose, pullulan, carboxyl methyl cellulose (CMC), and acrylonitrile styrene butadiene copolymer. . The weight ratio of the acrylic copolymer and the added binder may be from 9: 1 to 3: 7, specifically from 9: 1 to 5: 5, more specifically from 8: 2 to 6: 4. Within the above range, the shape stability is further improved, and it is possible to manufacture a battery having a highly efficient charge / discharge characteristic. For example, when a PVdF binder is additionally included, the PVdF binder may have a weight average molecular weight (Mw) of 500,000 to 1,500,000 g / mol. The PVdF binder may be a homopolymer or a co-polymer, and the copolymer may be PVdF-HFP, for example. In addition, the PVdF binder may have a weight average molecular weight of 1,000,000 g / mol or more. Further, two or more different weight average molecular weights may be mixed and used. For example, one or more species having a weight average molecular weight of 1,000,000 g / mol or less and one or more species having a weight average molecular weight of 1,000,000 g / mol or more may be used in combination. Use of a PVdF binder within the molecular weight range improves the adhesion between the coating layer and the polyolefin-based substrate film, effectively suppressing heat-shrinking of the polyolefin-based film, which is weak to heat, and further improving the electrolyte impregnability It is possible to produce a battery in which an electric output can be efficiently produced by utilizing it.

Membrane in accordance with embodiments of the present invention is to position the membrane between the anode and the cathode, when On the 100 ℃ 10 chogan pressure pressed into the 20kgf / cm ² to 100kgf / cm ² eseo 130 ℃ to stand for 10 minutes MD and TD Direction compression shrinkage ratio may be 10% or less, respectively. Specifically, it may be 5% or less, more specifically 3% or less. The compression shrinkage ratio is low, so that the heat resistance and shrinkability of the separator are improved in an environment in which the separator is used, thereby improving the safety of the battery. That is, a separation membrane having excellent shape stability can be provided. A method of measuring the compression shrinkage ratio of the separator is as follows: A sample of the separator is prepared as 50 mm in width (MD) and 50 mm in length (TD), the anode and the cathode are cut to 55 mm 55 mm, Cut the aluminum pouch used to make the battery into 6cm x 6cm. The anode, separator, and cathode are then placed in turn in an aluminum pouch folded in half. The sample is pressed at 100 ° C for 10 seconds under a pressure of 20 kgf / cm ² to 100 kgf / cm ² , left at 130 ° C for 10 minutes, and the shrinkage rate is obtained.

The separation membrane according to the embodiments of the present invention may have an air permeability of 500 sec / 100cc or less, specifically 50 to 400 sec / 100cc, more specifically 50 to 300 sec / 100cc. The tensile strength in the MD direction of the separator according to the embodiments of the present invention may be 1750 kg / cm ² or more, and the tensile strength in the TD direction may be 1650 kg / cm ² or more, specifically, 1700 kg / cm ^{2 or} more. The separation membrane according to the embodiments of the present invention has excellent air permeability and excellent mechanical properties even though the compression shrinkage ratio is excellent.

Hereinafter, a method of manufacturing a separation membrane according to an embodiment of the present invention will be described. The method for producing a separator according to an embodiment of the present invention is a method for producing a separator comprising repeating units derived from a (meth) acrylate monomer and repeating units derived from a monomer containing an acetate group, such as vinyl acetate or allyl acetate monomer, on one surface or both surfaces of a polyolefin- A binder containing an acrylic copolymer having an acryl-based copolymer; Inorganic particles; And forming a coating layer with a coating composition comprising a solvent.

First, forming the coating composition may include mixing a binder containing an acrylic copolymer, a solvent, and inorganic particles and stirring at 10 to 40 占 폚 for 30 minutes to 5 hours. In this case, the solid content may be 10 to 20 parts by weight based on the coating composition, and the weight ratio of the binder and the inorganic particles in the solid content may be 3: 7 to 0.1: 9.9.

Alternatively, an inorganic dispersion liquid in which the inorganic particles are dispersed in a dispersion medium may be prepared, and the dispersion may be mixed with a binder solution containing an acrylic copolymer and a polymer solution containing a solvent to prepare a coating composition. When the inorganic dispersion is separately prepared as described above, the dispersibility of the inorganic particles and the binder and the stability of the liquid preparation can be improved. Thus, in another embodiment, in preparing the coating composition of the present invention, the binder component and the inorganic particles may each be prepared and mixed in a dissolved or dispersed state in a suitable solvent.

For example, a solution prepared by dissolving an acrylic copolymer, a polyvinylidene fluoride homopolymer and / or a polyvinylidene fluoride-hexafluoropropylene copolymer in a suitable solvent, and an inorganic dispersion in which inorganic particles are dispersed are respectively prepared , Followed by mixing them together with an appropriate solvent. For the mixing, a ball mill, a beads mill, a screw mixer, or the like may be used.

Next, a coating layer is formed on one side or both sides of the polyolefin-based film with the above-mentioned coating composition.

The method of coating the polyolefin-based substrate film using the coating agent is not particularly limited, and a method commonly used in the technical field of the present invention can be used. Non-limiting examples of the coating method include a dip coating method, a die coating method, a roll coating method, and a comma coating method. These may be applied alone or in combination of two or more methods. The coating layer of the separator of the present invention may be formed by, for example, a dip coating method.

The thickness of the coating layer in this embodiment may be 0.01 탆 to 20 탆, specifically 1 탆 to 10 탆, more specifically 1 탆 to 5 탆. It is possible to obtain an excellent thermal stability and adhesion by forming a coating layer having an appropriate thickness within the above-mentioned thickness range, and prevent the thickness of the entire separation membrane from becoming excessively thick, thereby preventing the internal resistance of the battery from increasing.

In the present invention, the drying of the coating layer can be performed by a method of drying by hot air, hot air, low-humidity air, vacuum drying, or irradiation of far-infrared rays or electron beams. The drying temperature may vary depending on the type of the solvent, but may be generally from 60 ° C to 120 ° C. Drying time may vary depending on the type of solvent but can be generally 1 minute to 1 hour. In embodiments, it may be dried at a temperature of 90 ° C to 120 ° C for 1 minute to 30 minutes, or for 1 minute to 10 minutes.

According to another aspect of the present invention, there is provided an electrochemical cell including a polyolefin-based porous separation membrane including the coating layer, and an anode and a cathode and filled with an electrolyte.

The type of the electrochemical cell is not particularly limited and may be a battery of a kind known in the technical field of the present invention.

The electrochemical cell of the present invention may specifically be a lithium secondary battery such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

The method for producing the electrochemical cell of the present invention is not particularly limited and a method commonly used in the technical field of the present invention can be used.

A non-limiting example of the method for producing the electrochemical cell is as follows: A polyolefin-based separator containing the coating layer of the present invention is placed between a positive electrode and a negative electrode of a battery, Can be manufactured.

The electrode constituting the electrochemical cell of the present invention can be produced by binding an electrode active material to an electrode current collector by a method commonly used in the technical field of the present invention.

Of the electrode active materials used in the embodiment of the present invention, the cathode active material is not particularly limited and a cathode active material conventionally used in the technical field of the present invention may be used. Non-limiting examples of the positive electrode active material include lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, and lithium composite oxide in combination thereof.

The negative electrode active material of the electrode active material used in one embodiment of the present invention is not particularly limited and an anode active material commonly used in the technical field of the present invention may be used.

Non-limiting examples of the negative electrode active material include a lithium adsorbent material such as lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite or other carbon materials, and the like . The electrode current collector used in one embodiment of the present invention is not particularly limited and an electrode current collector commonly used in the technical field of the present invention can be used.

Non-limiting examples of the positive electrode current collector material among the electrode current collectors include aluminum, nickel, or foil produced by a combination of these materials. As a non-limiting example of the cathode current collector material of the electrode current collector, copper, gold, nickel, a copper alloy, or a foil produced by a combination of these materials can be used.

The electrolytic solution used in the present invention is not particularly limited, and electrolytic solutions for electrochemical cells commonly used in the technical field of the present invention can be used.

The electrolytic solution may be a salt having a structure such as A ⁺ B ^- dissolved or dissociated in an organic solvent. Non-limiting examples of the A ⁺ include alkali metal cations such as Li ⁺ , Na ^+, or K ⁺ , or cations made of combinations thereof. Non-limiting examples of B ^- include PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N ₃ SO ₂ ) ₂ ^- or C (CF ₂ SO ₂ ) ₃ ^- , or an anion composed of a combination of these. Nonlimiting examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate Dipropyl carbonate (DPC), dimethyl sulfoxide (DMSO), acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran (THF), N-methyl- N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC) or gamma-butyrolactone (GBL). These may be used alone or in combination of two or more.

Hereinafter, the present invention will be described in more detail by describing Examples, Comparative Examples and Experimental Examples. However, the following examples, comparative examples and experimental examples are merely examples of the present invention and should not be construed as limiting the scope of the present invention.

Example

Example  1: Preparation of Coating Membrane

An acrylic copolymer binder polymerized in a ratio of 4/1/5 mol of butyl methacrylate (BMA), methyl methacrylate (MMA), and vinyl acetate (Vinyl Acetate, VAc) was dissolved in acetone, And a PVDF binder KF9300 (Mw: 1,000,000 to 1,200,000 g / mol) were dissolved in a mixed solvent of acetone and DMAc to prepare a second binder solution (solid content: 7% by weight) Respectively. Alumina (LS235, Japan light metal) was added to acetone in an amount of 25% by weight, followed by dispersion in a bead mill for 3 hours to prepare an alumina dispersion. The first and second binder solutions and the alumina dispersion were mixed so that the weight ratio of the acrylic binder to the PVdF binder was 7/3 so that the weight ratio of the binder solid content to the alumina solid content was 1/6, % Acetone was added to prepare a coating solution. On both sides of polyethylene fabric (SK Corp.) having a thickness of 12 탆, the above coating solution was coated to a thickness of 2 탆 to prepare a coating separation membrane having a total thickness of about 16 탆.

Example  2: Preparation of Coating Membrane

A 5 wt% solution in which an acrylic binder in which butyl methacrylate (BMA), methyl methacrylate (MMA), and vinyl acetate (VAc) were polymerized in a ratio of 4/1/5 mol was dissolved in acetone and a PVdF binder KF9300 A 10 wt% solution was prepared by dissolving a 7 wt% solution and a PVdF-HFP binder (21216 (Solvay), weight average molecular weight: 500,000 to 700,000 g / mol) dissolved in acetone, acetone and DMAc mixed solvent in acetone. Alumina (LS235, Japan light metal) was added to acetone in an amount of 25% by weight, followed by dispersion in a bead mill for 3 hours to prepare an alumina dispersion. The binder solution and the alumina dispersion were mixed so that the weight ratio of the acrylic binder to the KF9300 and 21216 binder was 5/3/2 so that the weight ratio of the binder solid content to the alumina solid content was 1/5, Acetone was added as much as possible to prepare a coating solution. On both sides of polyethylene fabric (SK Corp.) having a thickness of 12 탆, the above coating solution was coated to a thickness of 2 탆 to prepare a coating separation membrane having a total thickness of about 16 탆.

Example  3: Preparation of Coating Membrane

Example 1 was repeated except that butyl acrylate (BMA), methyl methacrylate (MMA) and allyl acetate (Allyl Acetate) were used as the acrylic binder in Example 1 at a molar ratio of 4/1/5. To prepare a coating separation membrane having a total thickness of about 16 占 퐉.

Example  4: Preparation of Coating Membrane

The procedure of Example 1 was repeated, except that the molar ratio of butyl methacrylate (BMA), acrylonitrile (AN), and vinyl acetate (4/1/5) was used as the acrylic binder A coating film having a total thickness of about 16 탆 was prepared.

Example  5: Preparation of Coating Membrane

A separator was prepared in the same manner as in Example 1, except that the PVdF binder was not used and only the acrylic copolymer binder was used so that the weight ratio of the binder solid component to the alumina solid component was 1/6.

Comparative Example  1: Preparation of Coating Membrane

A 7 wt% solution of PVDF binder KF9300 dissolved in acetone and DMAc mixed solvent and a 10 wt% solution of 21216 binder dissolved in acetone were prepared. Alumina (LS235, Japan light metal) was added to acetone in an amount of 25% by weight, followed by dispersion in a bead mill for 3 hours to prepare an alumina dispersion. The binder solution and the alumina dispersion were mixed so that the weight ratio of the binder solid component to the alumina solid component was 1/6 so that the weight ratio of the above KF9300 and 21216 binder was 5/5. Acetone was added so that the total solid content was 11 wt% To prepare a coating solution. A coating separator having a total thickness of about 16 占 퐉 was prepared using a coating solution of polyethylene fabric (SK Corp.) having a thickness of 12 占 퐉.

Comparative Example  2: Preparation of membrane

A coating separation membrane having a total thickness of about 16 탆 was prepared in the same manner as in Example 1 except that polybutyl methacrylate (PBMA) was used as the acrylic binder in Example 1.

Comparative Example  3: Preparation of membrane

In Comparative Example 3, a polyethylene fabric (SK Company) having the same thickness as that used in Comparative Example 1 was used without being coated.

The composition of each separation membrane or separation membrane coating according to Examples 1 to 5 and Comparative Examples 1 to 3 is shown in Table 1 below.

Fabric / Thickness (㎛) Binder composition In the coating layer
Inorganic particle content Example 1 PE / 12 Acrylic / PVdF binder, 70/30% BMA + MMA + VAc 86 wt% Example 2 PE / 12 Acrylic / PVdF binder + PVdF-HFP, 50/50% BMA + MMA + VAc 83 wt% Example 3 PE / 12 Acrylic / PVdF binder, 70/30% BMA + MMA + allyl Ac 86 wt% Example 4 PE / 12 Acrylic / PVdF binder, 70/30% BMA + AN + VAc 86 wt% Example 5 PE / 12 Acrylic, 100% BMA + MMA + VAc 86 wt% Comparative Example 1 PE / 12 PVdF binder + PVdF-HFP, 100% 86 wt% Comparative Example 2 PE / 12 PBMA / PVdF binder, 70/30% 86 wt% Comparative Example 3 PE / 12 - -

Experimental Example

The permeability of the separator prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was measured by the measurement method described below. The tensile strength; The shrinkage ratio in the positive electrode, separator and negative electrode structures was measured during non-squeezing and pressing, and the results are shown in Table 2.

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Thickness (㎛) 16 16 16 16 16 16 16 12 Air permeability (sec / 100cc) 198 195 291 202 183 209 1320 140 Tensile strength (kgf / cm ² ) MD 1790 1794 1786 1803 1750 1807 1792 1765 TD 1713 1705 1698 1712 1684 1709 1713 1680 Non-squeeze shrinkage%)
(Left at 130 DEG C for 10 minutes) MD 16 15 17 18 19 13 16 24 TD 11 10 12 12 15 8 11 23 Compression Shrinkage (%)
(100 DEG C, 10 seconds, 20 kgf / cm < ² > pressure, left at 130 DEG C for 10 minutes) MD 2 One 2 2 2 15 4 24 TD 2 One One 2 One 8 2 22

1. Ventilation

Each of the separation membranes prepared in the above Examples and Comparative Examples was cut into 10 samples at a different size so that a circle having a diameter of 1 inch could be entered. Then, 10 samples were cut and measured with an air permeability measuring device The time for passing 100 cc of air through each of the samples was measured. The time was measured five times each, and then an average value was calculated to determine the aeration degree.

2. The tensile strength

Each of the separation membranes prepared in the above Examples and Comparative Examples was cut in a rectangular shape of 50 mm in length (MD), 150 mm in length (TD) and 50 mm in width (MD) Ten samples were prepared, each sample was mounted on a UTM (tensile tester), and the sample was squeezed to a measurement length of 20 mm. The average tensile strength in the MD and TD directions was measured by pulling the sample.

3. Crimping in anode, separator and cathode structures and Non-squeezed  Shrinkage rate

Each of the separators prepared in the above Examples and Comparative Examples was divided into 50 mm width × 50 mm width length by using a lithium cobalt oxide (LCO) cathode active material / binder styrene butadiene rubber (SBR) + carboxymethyl cellulose (CMC) / conductive material (carbonblack) = 95 / 2.5 / 2.5) and negative graphite (anode active material / binder (styrene butadiene rubber (SBR) + carboxymethyl cellulose (CMC) 5% (carbon black) = 98/1/1) are cut into 55 mm × 55 mm, respectively. Cut the aluminum pouch used to make the battery into 6cm x 6cm. Put them in an aluminum pouch folded in half, folded up in order of anode, separator and cathode.

The compression shrinkage rate was determined by measuring five points at regular intervals in the separator, pressing at a pressure of 20 kgf / cm < ² > at 100 DEG C for 10 seconds, leaving at 130 DEG C for 10 minutes, The compression shrinkage percentage was obtained.

The non-squeezing shrinkage ratio was measured by measuring the shrinkage of the separator after leaving the sample in an oven at 130 ° C for 10 minutes.

As can be seen from the above Table 2, the shrinkage ratio of Comparative Example 3, which is a separator fabric without a coating layer, is high regardless of whether or not the shrinkage occurs. In Comparative Example 1 or 2, Respectively. On the other hand, in the case of the separators of Examples 1 to 5 containing an acrylic copolymer containing a repeating unit derived from a (meth) acrylate and a monomer containing an acetate group, the compression shrinkage rate was greatly reduced as compared with the non- .

Claims (13)

A polyolefin-based substrate film, and
And a coating layer formed on one or both surfaces of the base film, the coating layer comprising an organic binder and inorganic particles,
Wherein the organic binder comprises an acrylic copolymer comprising a repeating unit derived from a (meth) acrylate monomer and a repeating unit derived from an acetate group containing monomer. The separation membrane according to claim 1, wherein the acetate-group-containing monomer-derived repeating unit is at least one monomers derived from vinyl acetate and allyl acetate. The separation membrane according to claim 2, wherein the acrylic copolymer has a glass transition temperature of less than 100 ° C. The separation membrane according to claim 1, wherein the inorganic particles are 70 to 99% by weight based on the total weight of the coating layer. The organic binder according to claim 1, wherein the organic binder is selected from the group consisting of polyvinylidene fluoride homopolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl Cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethylcellulose, carboxymethylcellulose, carboxymethylcellulose, carboxymethylcellulose, carboxymethylcellulose, And an acrylonitrile styrene butadiene copolymer. ≪ RTI ID = 0.0 > 11. < / RTI > The positive resist composition according to claim 1, wherein the repeating unit derived from the (meth) acrylate monomer is at least one selected from the group consisting of butyl (meth) acrylate, propyl (meth) acrylate, ethyl (meth) acrylate and methyl Which is a repeating unit derived from at least one selected monomer. The separator according to claim 1, wherein the acrylic copolymer is prepared by polymerizing the (meth) acrylate monomer and the acetate group-containing monomer in a molar ratio of 3: 7 to 7: 3. A polyolefin-based substrate film, and
And a coating layer formed on one or both surfaces of the base film, the coating layer comprising an organic binder and inorganic particles,
The separation membrane between the anode and the cathode was pressed at 100 ° C for 10 seconds under a pressure of 20 kgf / cm ² to 100 kgf / cm ² , and then the compression shrinkage rate in the longitudinal direction and the width direction of the separator was 10% or less ,
Wherein the separation membrane has an air permeability of 500 sec / 100cc or less. The separation membrane according to claim 8, wherein the separation membrane has a tensile strength in the MD direction of 1750 kg / cm ² or more and a tensile strength in the TD direction of 1650 kg / cm ² or more. The separation membrane according to claim 8, wherein the organic binder comprises an acrylic copolymer comprising a repeating unit derived from a (meth) acrylate system and an acetate group-containing monomer. 11. The method of claim 10, wherein the organic binder is selected from the group consisting of polyvinylidene fluoride homopolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl Cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethylcellulose, carboxymethylcellulose, carboxymethylcellulose, carboxymethylcellulose, carboxymethylcellulose, And an acrylonitrile styrene butadiene copolymer. ≪ RTI ID = 0.0 > 11. < / RTI > An electrochemical cell comprising the separator according to any one of claims 1 to 11. The electrochemical cell according to claim 12, wherein the electrochemical cell is a lithium secondary battery.