KR101742653B1 - Separator comprising acrylic copolymer having high-gelation properties and electrochemical battery comprising the separator - Google Patents

Abstract

The porous adhesive layer includes a first repeating unit derived from an acrylic monomer and a second repeating unit derived from an acrylic monomer containing a furfuryl group, wherein the porous adhesive layer comprises a porous substrate and a porous adhesive layer formed on one or both surfaces of the porous substrate, Wherein the acrylic copolymer has a glass transition temperature of 0 ° C to 30 ° C, and an electrochemical cell including the separator.

Description

TECHNICAL FIELD [0001] The present invention relates to a separator comprising an acrylic copolymer having a high gelation property, and an electrochemical cell including the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a separator having excellent electrolyte-impregnating property and adhesion to a substrate or an electrode, and an electrochemical cell including the separator.

2. Description of the Related Art [0002] Portable electronic devices such as video cameras, cellular phones, and portable computers are generally made lighter and more sophisticated, and a lot of research has been conducted on secondary batteries used as driving power sources. Examples of such a secondary battery include a nickel-cadmium battery, a nickel-hydrogen battery, a nickel-zinc battery, and a lithium secondary battery. Of these, lithium secondary batteries are used in many fields because of their small size and large size, high operating voltage, and high energy density per unit weight.

A separator for an electrochemical cell means an interlayer capable of charging and discharging the battery by keeping the ion conductivity constant while isolating the positive electrode and the negative electrode from each other in the battery.

Due to the increase in the area of the separator due to the increase in the size of the separator in the environment of the secondary battery or the increase in the weight of the separator or the use of an exterior material having a poor shape preservation such as a pouch type, the separation membrane wound between the electrode and the electrode may be detached, The adhesion between the separator and the electrode and between the separator and the substrate is required to be increased.

In this connection, it has been known to form an organic / inorganic mixed coating layer on one side or both sides of a base film of a separator (Korean Patent Registration No. 10-0775310) in order to improve the adhesion between the separator and the electrode, By including the inorganic particles, the adhesive force between the separation membrane coating material and the separation membrane substrate is weakened, and the coated materials are easily peeled off from the substrate.

Therefore, it has an adhesive force applicable to a secondary battery using an external material that can cause a shape change such as a large-sized secondary battery or a pouch type, and prevents deterioration of performance of the battery after charging and discharging, It is necessary to develop a secondary battery capable of maintaining the adhesive strength.

Korean Registered Patent No. 10-0775310 (published on November 11, 2007)

none

Disclosed herein is a separator having an improved ion conductivity and an excellent adhesion to a substrate, a positive electrode or a negative electrode, which is improved in swelling degree with respect to an electrolytic solution, and is excellent in shape stability of a battery upon charge and discharge, and an electrochemical cell using the same. .

According to an embodiment of the present invention, there is provided a separation membrane including a porous substrate and a porous adhesive layer formed on one or both surfaces of the porous substrate, wherein the porous adhesive layer comprises a first repeating unit derived from an acrylic monomer, And a second recurring unit derived from a monomer, wherein the acrylic copolymer has a glass transition temperature of 0 캜 to 30 캜.

According to another embodiment of the present invention, there is provided a separation membrane comprising a porous substrate and a porous adhesive layer formed on one or both surfaces of the porous substrate, wherein the porous adhesive layer comprises an acrylic copolymer having a furfuryl group, A separation membrane having an adhesive strength of 200 mN / 25 mm or more is provided.

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

The separator according to an embodiment of the present invention is excellent in adhesion to a porous substrate or a negative electrode and a positive electrode, thereby preventing deterioration of the performance of the battery due to a decrease in adhesion. In addition, the electrolytic solution impregnation rate of the separator is improved, and the electrolytic solution is retained in the porous adhesive layer to have a high electrolyte ion conduction ability, thereby improving the cell performance. In addition, a separator which can minimize changes in battery shape in an environment in which the battery is repeatedly expanded and contracted as the battery is repeatedly charged and discharged, secures a short ion transmission distance and improves the output efficiency of the battery, Battery can be provided.

1 is an exploded perspective view of an electrochemical cell according to an example.

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.

According to an embodiment of the present invention, there is provided a separation membrane including a porous substrate and a porous adhesive layer formed on one or both surfaces of the porous substrate, wherein the porous adhesive layer comprises a first repeating unit derived from an acrylic monomer, And a second recurring unit derived from a monomer, wherein the acrylic copolymer has a glass transition temperature of 0 캜 to 30 캜.

The porous substrate may have a plurality of pores and may be a porous substrate that can be used in an electrochemical device. Porous substrates include but are not limited to polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide , A polyimide imide, a polybenzimidazole, a polyether sulfone, a polyphenylene oxide, a cyclic olefin copolymer, a polyphenylene sulfide, and a polyethylene naphthalene, or a mixture of two or more thereof Lt; / RTI > In one example, the porous substrate may be a polyolefin-based substrate, and the polyolefin-based substrate is excellent in shut down function, thereby contributing to safety improvement of the cell. The polyolefin-based substrate may be selected from the group consisting of, for example, 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. In another example, the polyolefin-based resin may include, in addition to the olefin resin, a non-olefin resin or a copolymer of an olefin and a non-olefin monomer. The thickness of the porous substrate may be from 1 탆 to 40 탆, specifically from 5 to 20 탆, more specifically from 5 탆 to 16 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 air permeability of the porous substrate is 250 sec / 100cc or less, specifically 200 sec / 100cc or less, more specifically 150 sec / 100cc and porosity is 30% to 80%, specifically 40% to 60% .

The porous adhesive layer may include an acrylic copolymer containing a first repeating unit derived from an acrylic monomer and a second repeating unit derived from an acrylic monomer containing a furfuryl group. The glass transition temperature of the acrylic copolymer may range from 0 ° C to 30 ° C. When an acrylic copolymer having a glass transition temperature in the above range is used, the adhesive strength between the porous adhesive layer and the porous substrate and the adhesive strength between the porous adhesive layer and the anode or the cathode are enhanced, thereby providing a battery with little change in shape after charge and discharge. Specifically repeating units derived from an acrylic monomer having a glass transition temperature of the homopolymer of 30 ° C or lower, specifically 0 ° C to 25 ° C, repeating units derived from an acrylic monomer having a glass transition temperature of 80 ° C or higher, specifically 80 ° C to 110 ° C, And an acrylic copolymer containing an acrylic monomer-derived repeating unit containing a furfuryl group. It is possible to provide an acrylic copolymer having good adhesion and heat resistance by including two kinds of monomer-derived repeating units having different glass transition temperatures of the homopolymer. The 'glass transition temperature of the homopolymer' in an acrylic monomer having a glass transition temperature of 30 ° C. or lower or an acrylic monomer having a glass transition temperature of 80 ° C. or higher of the homopolymer is obtained by homopolymerizing the corresponding acrylic monomers Quot; glass transition temperature " For example, the homopolymerization may be carried out by, for example, introducing the acrylic monomers into a reactor in which nitrogen gas is refluxed, then introducing a solvent such as acetone, purging nitrogen gas for oxygen removal, An initiator such as a peroxide compound such as benzoyl peroxide or an azo compound such as azobisisobutyl nitrile is added while maintaining the temperature at 45 to 70 DEG C and polymerization reaction is carried out for 10 to 60 hours to obtain a homopolymer .

Examples of the acrylic monomer having a glass transition temperature of 30 占 폚 or less of the homopolymer include n-butyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (Meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (Meth) acrylate, and lauryl (meth) acrylate, but is not limited thereto.

Examples of the acrylic monomer having a glass transition temperature of 80 DEG C or higher of the homopolymer may include at least one member selected from the group consisting of methyl (meth) acrylate, isobonyl (meth) acrylate and cyclohexyl acrylate, But is not limited to.

An example of the acrylic monomer containing the furfuryl group may be the compound of the formula (1).

[Chemical Formula 1]

In Formula 1,

는 전부 포화되거나, 부분 불포화 또는 전부 불포화된 헤테로탄화수소고리를 나타내고, R₁은 치환되거나 비치환된 (CH₂)n일 수 있고, 여기서 n은 1 내지 10의 정수일 수 있다. R₁이 하나 이상의 치환기로 치환되는 경우 그 치환기는 각각 독립적으로, 할로겐 원자(F, Br, Cl, I), 히드록시기, 알콕시기, 니트로기, 시아노기, 아미노기, 아지도기, 아미디노기, 히드라지노기, 히드라조노기, 카르보닐기, 카르바밀기, 티올기, 에스테르기, 카르복실기 또는 그의 염, 술폰산기 또는 그의 염, 인산기 또는 그의 염, C₁ 내지 C₂₀ 알킬기, C₂ 내지 C₂₀ 알케닐기, C₂ 내지 C₂₀ 알키닐기, C₆ 내지 C₃₀ 아릴기, C₇ 내지 C₃₀ 아릴알킬기, C₁ 내지 C₂₀ 알콕시기, C₁ 내지 C₂₀ 헤테로알킬기, C₃ 내지 C₂₀ 헤테로아릴알킬기, C₃ 내지 C₂₀ 사이클로알킬기, C₃ 내지 C₂₀ 사이클로알케닐기, C₄ 내지 C₂₀ 사이클로알키닐기, C₂ 내지 C₂₀ 헤테로사이클로알킬기일 수 있다.

Represents a fully saturated, partially unsaturated or fully unsaturated heterohydrocarbon ring, and R ₁ can be substituted or unsubstituted (CH ₂ ) n, wherein n can be an integer from 1 to 10. When R ₁ is substituted with one or more substituents, the substituents are each independently selected from the group consisting of a halogen atom (F, Br, Cl, I), a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino group, an azido group, A carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C ₁ to C ₂₀ alkyl group, a C ₂ to C ₂₀ alkenyl group, a cyano group, a cyano group, C ₂ to C ₂₀ alkynyl groups, C ₆ to C ₃₀ aryl groups, C ₇ to C ₃₀ arylalkyl groups, C ₁ to C ₂₀ alkoxy groups, C ₁ to C ₂₀ heteroalkyl groups, C ₃ to C ₂₀ heteroarylalkyl groups, C ₃ to C ₂₀ may be a cycloalkyl group, C ₃ to C ₂₀ cycloalkyl alkenyl, C ₄ to C ₂₀ cycloalkyl alkynyl group, C ₂ to C ₂₀ heterocycloalkyl group.

The acrylic monomer containing the furfuryl group may be, for example, furfuryl (meth) acrylate or tetrahydrofurfuryl (meth) acrylate. The acrylic copolymer includes an acrylic monomer-derived repeating unit containing the furfuryl group, so that the impregnating property or swelling property of the porous adhesive layer can be improved. The swelling property means the degree to which the acrylic copolymer absorbs and swells the electrolyte solution. Although not wishing to be bound by any particular theory, it is believed that the furfuryl group has a high electronegativity and thus has affinity for lithium ions in the electrolyte solution, thereby improving the electrolyte impregnating property or swelling property of the porous adhesive layer. When the electrolyte impregnating property or the swelling property is increased, the electrolyte can be retained in the porous adhesive layer, and the electrolyte may have a high electrolyte ion conduction capability, thereby improving battery performance. Therefore, the separation membrane disclosed herein can improve the electrolyte ion conduction ability due to the high electrolyte impregnation property of the porous adhesive layer.

The acrylic copolymer may be prepared by polymerizing an acrylic monomer containing an acrylic monomer and a furfuryl group. Specifically, the acrylic copolymer may be prepared by polymerizing an acrylic monomer having a glass transition temperature of 30 占 폚 or less of a homopolymer, an acrylic monomer having a glass transition temperature of 80 占 폚 or higher of a homopolymer, and an acrylic monomer containing a furfuryl group. The polymerization method is not particularly limited and a method known to those skilled in the art can be used. For example, the acrylic monomers may be introduced into the reactor at a suitable weight ratio, and then a solvent such as acetone or deionized water may be added, An initiator such as a peroxide-based initiator such as ammonium persulfate or benzoyl peroxide or an azo-based compound such as azobisisobutylnitrile is added while maintaining the temperature at 45 to 70 ° C at 50 to 100 ° C for 1 to 30 hours Lt; / RTI > The content of each monomer used for preparing the acrylic copolymer may be 25 to 80% by weight of the acrylic monomer, and 5 to 60% by weight of the acrylic monomer containing the furfuryl group based on the total weight of the monomers . In one example, the homopolymer has 20 to 50% by weight of an acrylic monomer having a glass transition temperature of 30 DEG C or lower, 3 to 25% by weight of an acrylic monomer having a glass transition temperature of 80 DEG C or higher of the homopolymer, And 5 to 60% by weight of an acrylic monomer. More specifically, the homopolymer has 30 to 50% by weight of an acrylic monomer having a glass transition temperature of 30 DEG C or less, 5 to 15% by weight of an acrylic monomer having a glass transition temperature of 80 DEG C or more of the homopolymer, The acrylic monomer may be 5 to 50% by weight. In a more specific example, the acrylic monomer having a glass transition temperature of 30 DEG C or lower, the acrylic monomer having a glass transition temperature of 80 DEG C or higher and the acrylic monomer having a furfuryl group may be used in an amount of 3 to 5: In a weight ratio of 1.5: 1 to 6.5. If the monomer content is in the above range, it is advantageous in terms of electrolyte impregnability, adhesion to electrodes and porous substrate. The glass transition temperature of the acrylic copolymer may be 0 to 30 캜, specifically 0 to 25 캜, more specifically 0 to 20 캜. Within this range, the acrylic copolymer forms good adhesion with the electrode of the separation membrane or with the porous base material, thereby securing the form stability. The weight average molecular weight (Mw) of the acrylic copolymer may be 10,000 to 1,000,000. Specifically, it may be 30,000 to 700,000. When the acrylic copolymer within the above molecular weight range is used, the adhesion between the porous adhesive layer and the porous substrate is strengthened, and the shape stability of the separation membrane can be improved. Also, it is possible to produce a separator having a sufficiently improved impregnation property of an electrolytic solution, and it is advantageous to produce a cell in which an electric output is efficiently generated.

The separation membrane according to another embodiment of the present invention may further contain an acetate group-containing monomer-derived repeating unit in the acrylic copolymer of the porous adhesive layer. The repeating unit derived from an acetate group-containing monomer may be a repeating unit represented by the following formula (2)

 (2)

In Formula 2,

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,

For example, the repeating unit derived from an acetate group-containing monomer may be a repeating unit derived from an acetate group-containing monomer selected from the group consisting of vinyl acetate and allyl acetate. The acrylic copolymer is obtained by polymerizing the above-mentioned acrylic monomers and an acetate group-containing monomer such as vinyl acetate and / or allylacetate in a weight ratio of 9.9: 0.1 to 5: 5, specifically 9: 1 to 6: 4 . The acetate group-containing monomer may be used in an amount of 0.1 to 50% by weight, more specifically 0.1 to 20% by weight, based on the total weight of the monomers used for preparing the acrylic copolymer. When it is used in the above range, it is advantageous in terms of electrolyte non-solubility of the acrylic copolymer and adhesion strength to an electrode or a porous substrate.

The prepared acrylic copolymer is dissolved or mixed in a solvent to prepare a porous adhesive layer composition solution. The solvent used for preparing the porous adhesive layer composition solution is not particularly limited as long as it is a solvent capable of dissolving the acrylic copolymer. Non-limiting examples of the solvent usable in the present invention include acetone, dimethyl formamide, dimethyl sulfoxide, dimethylacetamide, dimethyl carbonate or N-methylpiperazine. N-methylpyrrolone, cyclohexane, and the like. The content of the solvent based on the weight of the porous adhesive layer composition may be 20 to 99% by weight, specifically 50 to 95% by weight, and more specifically 70 to 95% by weight. When the solvent is contained in the above range, the porous adhesive layer composition can be easily produced and the heat resistant layer can be smoothly dried.

The separation membrane according to another embodiment of the present invention may further contain other kinds of organic binders in addition to the acrylic copolymer according to the above embodiment in the porous adhesive layer. Is substantially the same as the separator according to the embodiment of the present invention, except that the porous adhesive layer further comprises an organic binder. Therefore, in the following, other binders included in addition to the acrylic copolymer will be mainly described. In the present embodiment, the adhesive strength and heat resistance of the separator can be further improved by further including another binder. Examples of the binder that can be added in addition to the acrylic copolymer include vinylidene fluoride such as polyvinylidene fluoride (PVdF) homopolymer and polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene oxide, cellulose acetate, polyvinylpyrrolidone, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, But are not limited to, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethyl cellulose, Ethyl sucrose (cyanoethylsu crose, pullulan, carboxyl methyl cellulose, and acrylonitrile styrene-butadiene copolymer, or a mixture thereof. More specifically, a polyvinylidene fluoride (PVdF) homopolymer or a polyvinylidene fluoride-based copolymer may be used. The polyvinylidene fluoride copolymer may include polyvinylidene fluoride-hexafluoro Propylene (polyvinylidene fluoride-Hexafluoropropylene copolymer, PVdF-HFP). The term "polyvinylidene fluoride homopolymer" as used herein means a polymer containing only VDF-derived repeating units as repeating units, and the polyvinylidene fluoride copolymer includes at least two kinds of repeating units other than VDF- ≪ / RTI > or more of the repeating units. The PVdF binder may have a weight average molecular weight (Mw) ranging from 300,000 to 1,700,000. Use of a PVdF binder within the molecular weight range enhances the adhesive force between the adhesive layer and the porous substrate to effectively suppress shrinkage of the porous substrate that is resistant to heat and to improve the electrolyte impregnability, And there is an advantage that the battery can be produced efficiently by utilizing the electric power.

The weight ratio of the acrylic copolymer to the additional binder may be 9: 1 to 4: 6. Specifically 8: 2 to 5: 5, more specifically 8: 2 to 6: 4. When used within this range, it is possible to produce an electrochemical cell having excellent shape stability while maintaining sufficient adhesion of the separator. As a result, deterioration in the performance of the produced battery can be prevented, and the battery can have charge / discharge characteristics of high efficiency.

The separation membrane according to another embodiment of the present invention may further include inorganic particles in the porous adhesive layer. The inorganic particles used in the present invention are not particularly limited and inorganic particles commonly used in the art can be used. Non-limiting examples of the inorganic particles usable in the present invention include Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ , Ga ₂ O ₃ , TiO _2, and 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 the present invention is not particularly limited, but may be an average particle diameter of 1 to 2,000 nm, for example, 100 to 1,000 nm. It is possible to prevent degradation of the dispersibility of the inorganic particles in the porous adhesive layer and the processability of forming the porous adhesive layer and to appropriately control the thickness of the porous adhesive layer, An increase in resistance can be prevented. In addition, the size of the pores generated in the porous adhesive layer is appropriately controlled, thereby reducing the probability of an internal short circuit occurring during charging and discharging of the battery.

In the porous adhesive layer, the inorganic particles may be contained in an amount of 60 to 95% by weight, specifically 75 to 90% by weight, more specifically 80 to 90% by weight, based on the total weight of the porous adhesive layer. When inorganic particles are contained within the above range, the heat radiation characteristics of the inorganic particles can be sufficiently exhibited.

The method of forming the porous adhesive layer on the porous substrate is not particularly limited, and a method commonly used in the technical field of the present invention such as a coating method, a lamination method, and a coextrusion method 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 porous adhesive layer of the separator of the present invention may be formed by, for example, a dip coating method. The porous adhesive layer may be formed on one side or both sides of the porous substrate, and the thickness thereof may be in the range of 1 μm to 10 μm, specifically 1 μm to 6 μm.

According to another embodiment of the present invention, there is provided a separation membrane including a porous substrate and a porous adhesive layer formed on one or both sides of the porous substrate, wherein the porous adhesive layer comprises an acrylic copolymer having a furfuryl group, Is 200 mN / 25 mm or more, respectively. The acrylic copolymer having a furfuryl group may be a copolymer having a repeating unit derived from a compound represented by the following formula (1).

[Chemical Formula 1]

In Formula 1,

는 전부 포화되거나, 부분 불포화 또는 전부 불포화된 헤테로탄화수소고리를 나타내고, R₁은 치환되거나 비치환된 (CH₂)n일 수 있고, 여기서 n은 1 내지 10의 정수일 수 있다. 일 예에서, 상기 아크릴계 공중합체는 상기 실시예에 설명한 것과 동일한 아크릴계 공중합체일 수 있다.

Represents a fully saturated, partially unsaturated or fully unsaturated heterohydrocarbon ring, and R ₁ can be substituted or unsubstituted (CH ₂ ) n, wherein n can be an integer from 1 to 10. In one example, the acrylic copolymer may be the same acrylic copolymer as described in the above embodiment.

The positive electrode or negative electrode adhesion force means an adhesion force between the separator and the anode or the cathode. The anodic or cathodic adhesive strength can be measured by a known method, and in one example, it can be measured by the following method, but it is not limited thereto. The test shall be carried out in accordance with Clause 8 of Korean Industrial Standard KS-A-01107 (Test Method for Adhesive Tape and Adhesive Sheet). The separator film is used as a test piece with a width of 25 mm and a length of 250 mm, and a tape (nitto 31B) is attached to one surface of the separator to complete the test piece. On the other side of the separator, a cathode film (LCO (lithium cobalt oxide) cathode active material / binder styrene butadiene rubber (SBR) + carboxymethyl cellulose (CMC) / carbon black = 95 / 2.5 / 2.5) A film (natural graphite anode active material / binder (styrene butadiene rubber (SBR) + carboxymethyl cellulose (CMC) 5% / conductive black 98/1/1) / Min. ≪ / RTI > After a lapse of 30 minutes from the pressing, one side of the test piece was turned 180 ° to peel off about 25 mm, and a tape 31B attached to one side of the separating film and the separating film was attached to the upper clip of the tensile strength device, Is fixed to the lower clip, and pulled at a pulling rate of 60 mm / min to measure the pressure when the anode or the cathode film is peeled off from the separator. The tensile strength tester uses, for example, Instron Series IX / s Automated materials Tester-3343.

Specifically, the anode adhesive force may be 200 mN / 25 mm to 500 mN / 25 mm, and specifically 200 mN / 25 mm to 400 mN / 25 mm. Within this range, the separator and the anode can be sufficiently bonded. Accordingly, as the battery including the separator is repeatedly charged and discharged, the change of the battery shape can be minimized in an environment where the expansion and contraction of the battery are repeated, and the output efficiency of the battery can be improved by securing a short ion transfer distance . The negative electrode adhesive force may be 200 mN / 25 mm or more, specifically 200 mN / 25 mm to 400 mN / 25 mm, and specifically 200 mN / 25 mm to 300 mN / 25 mm. Within this range, the separation membrane can be sufficiently adhered to the cathode. Accordingly, as the battery including the separator is repeatedly charged and discharged, the change of the battery shape can be minimized in an environment where the expansion and contraction of the battery are repeated, and the output efficiency of the battery can be improved by securing a short ion transfer distance .

The separation membrane according to the above examples may have a base adhesive strength of 700 mN / 25 mm or more, specifically 700 mN / 25 mm to 1300 mN / 25 mm. The substrate adhesive force refers to the adhesive force between the porous adhesive layer and the porous substrate. The adhesive strength of the substrate may be measured by the following method, but is not limited thereto: The test is performed in accordance with Clause 8 of Korean Industrial Standard KS-A-01107 (Test Method for Adhesive Tape and Adhesive Sheet). Each of the prepared membrane films was used as a test piece having a width of 25 mm and a length of 250 mm and a tape (nitto 31B) was attached to each side of the separation membrane to prepare a specimen. The specimen was then subjected to a reciprocating motion at a speed of 300 mm / And the specimen is squeezed. After 30 minutes, the specimen was turned 180 ° to peel off about 25 mm. The tape attached to one side of the membrane and membrane was placed on the upper clip of the Instron Series 1X / s Automated materials Tester-3343, Instron. . The tape attached to the other side of the separator is fixed to the lower clip and pulled at a pulling rate of 60 mm / min to measure the pressure when the porous adhesive layer is peeled from the porous substrate.

The substrate adhesive force may be 800 mN / 25 mm to 1250 mN / 25 mm, and more specifically, 900 mN / 25 mm to 1200 mN / 25 mm. Within the above range, the porous adhesive layer and the porous substrate are sufficiently bonded. Accordingly, as the battery including the separator is repeatedly charged and discharged, the change of the battery shape can be minimized in an environment where the expansion and contraction of the battery are repeated, and the output efficiency of the battery can be improved by securing a short ion transfer distance .

The separation membrane according to the embodiment may have an air permeability of 400 sec / 100cc or less, specifically 300 sec / 100cc or less, more specifically 250 sec / 100cc.

According to another embodiment of the present invention, cathode; A separator disclosed herein between the anode and the cathode; And a secondary battery comprising the electrolyte.

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

The secondary battery 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 secondary battery 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 manufacturing the secondary battery is as follows: A battery is manufactured in such a manner that a separation membrane including the porous adhesive layer of the present invention is placed between the anode and the cathode of a battery, .

1 is an exploded perspective view of an electrochemical cell according to an example. The electrochemical cell according to one embodiment is a secondary battery, and the present invention is not limited thereto, but may be applied to various types of batteries such as a pouch type battery, a lithium polymer battery, and a cylindrical battery.

Referring to FIG. 1, a secondary battery 100 according to an embodiment includes an electrode assembly 40 wound around a separator 30 between an anode 10 and a cathode 20, And a case 50 in which the case 50 is embedded. The anode 10, the cathode 20 and the separator 30 are impregnated with an electrolyte (not shown).

The separation membrane 30 is as described above.

The anode 10 may include a cathode current collector and a cathode active material layer formed on the cathode current collector. The cathode active material layer may include a cathode active material, a binder, and optionally a conductive material.

The cathode current collector may be aluminum (Al), nickel (Ni) or the like, but is not limited thereto.

As the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Concretely, at least one of cobalt, manganese, nickel, aluminum, iron or a composite oxide or composite phosphorus of a metal and lithium in combination thereof may be used. More specifically, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate or a combination thereof may be used.

The binder not only adheres the positive electrode active materials to each other well but also adheres the positive electrode active material to the positive electrode current collector. Specific examples thereof include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride , Carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like. These may be used alone or in combination of two or more.

The conductive material imparts conductivity to the electrode. Examples of the conductive material include, but are not limited to, natural graphite, artificial graphite, carbon black, carbon fiber, metal powder, and metal fiber. These may be used alone or in combination of two or more. The metal powder and the metal fiber may be made of metals such as copper, nickel, aluminum, and silver.

The cathode 20 may include a negative electrode collector and a negative electrode active material layer formed on the negative collector.

The negative electrode current collector may be copper (Cu), gold (Au), nickel (Ni), copper alloy, or the like, but is not limited thereto.

The negative electrode active material layer may include a negative electrode active material, a binder, and optionally a conductive material.

Examples of the negative electrode active material include a material capable of reversibly intercalating and deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, a transition metal oxide, Can be used.

Examples of the material capable of reversibly intercalating and deintercalating lithium ions include carbonaceous materials, and examples thereof include crystalline carbon, amorphous carbon, and combinations thereof. Examples of the crystalline carbon include amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke, and the like. As the lithium metal alloy, a lithium-metal alloy may be selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, An alloy of a selected metal may be used. As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-Y alloy, Sn, SnO ₂ , Sn-C composite, Sn- And at least one of them may be mixed with SiO ₂ . The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Se, Te, Po, and combinations thereof. Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The kinds of the binder and the conductive material used for the cathode are the same as those used for the anode and the conductive material.

The positive electrode and the negative electrode may be prepared by mixing each active material and a binder with a conductive material in a solvent to prepare each active material composition and applying the active material composition to each current collector. The solvent may be N-methyl pyrrolidone or the like, but is not limited thereto. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein.

The electrolytic solution includes an organic solvent and a lithium salt.

The organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specific examples thereof may be selected from a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent and an aprotic solvent.

Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate Carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Specifically, when a mixture of a chain carbonate compound and a cyclic carbonate compound is used, it can be prepared from a solvent having a high viscosity and a high dielectric constant. Here, the cyclic carbonate compound and the chain carbonate compound may be mixed in a volume ratio of 1: 1 to 1: 9.

Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate,? -Butyrolactone, decanolide, valerolactone, Mevalonolactone, caprolactone, and the like. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran and the like. Examples of the ketone-based solvent include cyclohexanone, and examples of the alcohol-based solvent include ethyl alcohol, isopropyl alcohol, and the like.

The organic solvents may be used alone or in combination of two or more. When two or more of them are used in combination, the mixing ratio may be appropriately adjusted according to the performance of the desired cell.

The lithium salt is dissolved in an organic solvent to act as a source of lithium ions in the cell to enable operation of a basic secondary cell and accelerate the movement of lithium ions between the positive electrode and the negative electrode.

For example the lithium salt _{is, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiN (SO 3 C 2 F 5) 2, LiN (CF 3 SO 2) 2, LiC 4 F 9 SO 3, LiClO 4, LiAlO 2 , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) where x and y are natural numbers, LiCl, LiI, LiB (C ₂ O ₄ ) _2, .

The concentration of the lithium salt can be used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolytic solution has an appropriate conductivity and viscosity, and thus can exhibit excellent electrolytic solution performance, and lithium ions can effectively move.

The secondary battery according to another example of the present invention may have a 100 cycle charge / discharge retention rate in the range of 70% to 100%, specifically 80% to 100%.

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

Manufacturing example  1: Preparation of first acrylic copolymer

Butylmethacrylate (BMA) (its homopolymer glass transition temperature: 20 占 폚), methyl methacrylate (MMA) (its homopolymer glass transition temperature: 100 占 폚), polyvinyl alcohol (Dodecyl sulfate) sodium salt (SDS, 85.0%) as an emulsifier and ammonium persulfate (sodium persulfate) as an emulsifying agent were added in a ratio of 4: 1: 5 by weight of tetrahydrofurfuryl acrylate (THF- ) (APS, 98.0%) was used as a polymerization initiator and 0.8% by weight and 0.3% by weight of the total amount of monomers were added, respectively. Thereafter, the mixed solution was put into a thermostatic chamber, stirred, heated to 75 캜 and reacted for 2 hours to synthesize an acrylic copolymer. The resulting emulsion was cooled to room temperature, and then added with stirring into an aqueous 2 wt% ammonium sulfate solution to obtain a precipitated polymer resin. The obtained polymer was separated from the solvent, washed with distilled water several times, and then dried to prepare a first acrylic copolymer having a weight average molecular weight of 45,000 and a glass transition temperature of 9 캜.

Manufacturing example  2: Preparation of Second Acrylic Copolymer

Except that BMA, MMA, THF-A and VAc were mixed in a weight ratio of 4: 1: 4: 1 by adding vinyl acetate (VAc) in addition to BMA, MMA and THF- A second acrylic copolymer having a glass transition temperature of 13.5 DEG C was prepared.

Manufacturing example  3: Production of tertiary acrylic copolymer

MMA, THF-A, and VAc were mixed in a ratio of 4: 1 (v / v) instead of BMA, MMA and THF-A in a weight ratio of 4: : 3: 2 in the weight ratio, a third acrylic copolymer having a glass transition temperature of 18.1 DEG C was prepared.

Manufacturing example  4: Preparation of the fourth acrylic copolymer

MMA, THF-A, and VAc were mixed in a ratio of 4: 1 (v / v) instead of BMA, MMA and THF-A in a weight ratio of 4: : 2: 3 in the weight ratio, a fourth acrylic copolymer having a glass transition temperature of 22.9 캜 was prepared.

Manufacturing example  5: Preparation of Fifth Acrylic Copolymer

MMA, THF-A, and VAc were mixed in a ratio of 4: 1 (v / v) instead of BMA, MMA and THF-A in a weight ratio of 4: : 1: 4 in the weight ratio, a fifth acrylic copolymer having a glass transition temperature of 27.8 캜 was prepared.

Manufacturing example  6: Preparation of the sixth acrylic copolymer

In Production Example 1, vinyl acetate (VAc) was added to the mixture of BMA, MMA, and VAc at a weight ratio of 4: 1: 5 without mixing BMA, MMA, and THF-A in a weight ratio of 4: To prepare a sixth acrylic copolymer having a glass transition temperature of 32.9 占 폚.

Example  1: Preparation of membrane

The first acrylic copolymer prepared in Preparation Example 1 was dissolved in acetone to prepare a first acrylic copolymer solution having a solid content of 10% by weight. 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. Thereafter, the acrylic copolymer solution and the alumina dispersion were mixed so that the solid content of the first acrylic copolymer and the alumina solid content were 1/6, and acetone was added so that the total solid content was 15% by weight to prepare the porous adhesive layer composition Respectively. On both sides of a polyethylene fabric (SK) having a thickness of 7 占 퐉, To prepare a separation membrane having a total thickness of about 9 mu m.

Example  2: Preparation of membrane

A separation membrane was prepared in the same manner as in Example 1, except that the second acrylic copolymer was used in place of the first acrylic copolymer.

Example  3: Preparation of membrane

A separation membrane was prepared in the same manner as in Example 1 except that the third acrylic copolymer was used instead of the first acrylic copolymer.

Example  4: Preparation of membrane

A separation membrane was prepared in the same manner as in Example 1 except that the fourth acrylic copolymer was used instead of the first acrylic copolymer.

Example  5: Preparation of membrane

A separation membrane was prepared in the same manner as in Example 1 except that the fifth acrylic copolymer was used instead of the first acrylic copolymer.

Example  6: Preparation of membrane

The first acrylic copolymer prepared in Preparation Example 1 was dissolved in acetone to prepare a first acrylic copolymer solution having a solid content of 10% by weight. 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. Thereafter, the mixture was mixed so that the weight ratio of the first acrylic copolymer solution to the PVdF binder (KF9300, Kureha, Mw: 1,200,000) was 7: 3, and the binder solution and the alumina , And acetone was added thereto so that the total solid content was 15% by weight to prepare a porous adhesive layer composition. On both sides of a polyethylene fabric (SK) having a thickness of 7 占 퐉, To prepare a separation membrane having a total thickness of about 9 mu m.

Example  7: Preparation of membrane

In Example 2, the weight ratio of the second acrylic polymer solution to the PVdF binder (KF9300, Kureha, Mw: 1,200,000) was adjusted to 7: 3, and the binder solution and the alumina solid were mixed so that the binder solid content and alumina solid content became 1/6. Alumina dispersion was used in place of the alumina dispersion.

Comparative Example  1: Preparation of membrane

The separation membrane of Comparative Example 1 was prepared in the same manner as in Example 1 except that the sixth acrylic copolymer was used instead of the first acrylic copolymer.

Comparative Example  2: Preparation of membrane

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. Thereafter, the first PVdF binder solution and the alumina dispersion were mixed so that the solid content of the PVdF binder (KF9300, Kureha, Mw: 1,200,000, Tg: -35 ° C) and the alumina solid content were 1/6, % By weight of acetone to prepare a porous adhesive layer composition. On both sides of a polyethylene fabric (SK) having a thickness of 7 占 퐉, To prepare a separation membrane having a total thickness of 9 탆.

The composition of each separator according to Examples 1 to 7 and Comparative Examples 1 and 2 is shown in Table 1 below.

Substrate / Thickness (탆) Binder composition Acrylic polymerization weight ratio Example 1 PE / 7 Acrylic, 100% BMA + MMA + THF-A 4: 1: 5 Example 2 PE / 7 Acrylic, 100% BMA + MMA + THF-A + VAc 4: 1: 4: 1 Example 3 PE / 7 Acrylic, 100% BMA + MMA + THF-A + VAc 4: 1: 3: 2 Example 4 PE / 7 Acrylic, 100% BMA + MMA + THF-A + VAc 4: 1: 2: 3 Example 5 PE / 7 Acrylic, 100% BMA + MMA + THF-A + VAc 4: 1: 1: 4 Example 6 PE / 7 Acrylic / PVdF system, 7/3 BMA + MMA + THF-A 4: 1: 5 Example 7 PE / 7 Acrylic / PVdF system, 7/3 BMA + MMA + THF-A + VAc 4: 1: 4: 1 Comparative Example 1 PE / 7 Acrylic, 100% BMA + MMA + VAc 4: 1: 5 Comparative Example 2 PE / 7 PVdF system, 100% - -

Experimental Example

The base adhesive strength, the anode adhesive strength, the anode adhesive strength, and the rate of change in thickness were measured for the separation membranes prepared in Examples 1 to 7 and Comparative Examples 1 and 2, and the results are shown in Tables 2 and 3 .

Substrate adhesion

The test was carried out in accordance with Clause 8 of Korean Industrial Standard KS-A-01107 (Test Method for Adhesive Tape and Adhesive Sheet). Each of the prepared membrane films was used as a test piece having a width of 25 mm and a length of 250 mm and a tape (nitto 31B) was attached to each side of the separation membrane to prepare a specimen. The specimen was then subjected to a reciprocating motion at a speed of 300 mm / And the specimen was squeezed. After 30 minutes, the specimen was turned 180 ° to peel off about 25 mm. The tape attached to one side of the membrane and membrane was placed on the upper clip of the Instron Series 1X / s Automated materials Tester-3343, Instron. Lt; / RTI &gt; The tape attached to the other side of the membrane was fixed to the lower clip and pulled at a pulling rate of 60 mm / min to measure the pressure when the porous adhesive layer was peeled from the porous substrate.

Anode adhesive force

The test was carried out in accordance with Clause 8 of Korean Industrial Standard KS-A-01107 (Test Method for Adhesive Tape and Adhesive Sheet). The prepared separator film was used as a test piece having a width of 25 mm and a length of 250 mm and a tape (nitto 31B) was attached to one side of the separator to prepare a specimen. On the other side, a positive electrode film (lithium cobalt oxide) cathode active material / binder styrene butadiene rubber (SBR) + carboxymethylcellulose (CMC) / carbon black = 95 / 2.5 / 2.5) was reciprocated once at a speed of 300 mm / min using a pressing roller having a load of 2 kg, thereby pressing the specimen . After 30 minutes, the specimen was turned 180 ° to peel off about 25 mm. The tape attached to one side of the membrane and membrane was placed on the upper clip of the Instron Series 1X / s Automated materials Tester-3343, Instron. Lt; / RTI &gt; The positive electrode film on the other side of the separator was fixed to the lower clip and pulled at a pulling rate of 60 mm / min to measure the pressure when the positive electrode film was peeled off from the separator.

Cathode adhesion

The test was carried out in accordance with Clause 8 of Korean Industrial Standard KS-A-01107 (Test Method for Adhesive Tape and Adhesive Sheet). Each of the prepared separator films was made into test pieces having a width of 25 mm and a length of 250 mm and a tape (nitto 31B) was attached to one side of the separator to form test pieces. On the other side, a negative graphite anode active material / binder (styrene butadiene rubber (SBR) + Carboxymethylcellulose (CMC) 5% / carbon black = 98/1/1)) was pressed and pressed once using a compression roller having a load of 2 kg at a speed of 300 mm / min. After 30 minutes, the specimen was turned 180 ° to peel off about 25 mm. The tape attached to one side of the membrane and membrane was placed on the upper clip of the Instron Series 1X / s Automated materials Tester-3343, Instron. Lt; / RTI &gt; The negative electrode film on the other side of the separator was fixed to the lower clip and pulled at a pulling rate of 60 mm / min to measure the pressure when the negative electrode film was peeled off from the separator.

Thickness change rate

The lithium secondary battery was assembled by using the separator obtained in the examples and the comparative examples and charged with a constant current until the voltage reached 4.2 V by a constant current constant voltage charging method at 60 DEG C and 1C, Followed by discharging to 3.0 V with a constant current of 1C. The charge / discharge cycle test was performed up to 500 cycles, and the change in thickness of the pouch cell after 500 cycles to the initial thickness was measured using a veneer caliper (500-180, MITUTOYO).

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Base Adhesion (mN / 25mm) 1207 1107 1046 988 926 1098 1007 797 600 Anode adhesive force (mN / 25 mm) 387 375 366 353 342 352 341 280 210 Cathode Adhesion (mN / 25mm) 231 225 218 214 210 210 205 172 110

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Thickness change ratio (%) 105 109 112 115 119 124 102

Referring to Tables 2 and 3, in Examples 1 to 7, the substrate adhesive force, the anode adhesive force and the anode adhesive force were all good, and the lower the Tg of the acrylic copolymer, the better the adhesive strength was. In the case of Comparative Example 1, good adhesion was obtained, but as shown in Table 3, the thickness change rate after 124 cycles was as high as 124%, causing external deformation of the battery. In the case of Comparative Example 2, although the rate of change in thickness after 500 cycles is as low as 102%, it does not have the base adhesive force necessary for the battery assembling process and can not be applied to the mass production process.

Claims (20)

Porous substrate, and
And a porous adhesive layer formed on one or both surfaces of the porous substrate,
Wherein the porous adhesive layer comprises an acrylic copolymer comprising a first repeating unit derived from an acrylic monomer and a second repeating unit derived from an acrylic monomer containing a furfuryl group,
Wherein the acrylic copolymer has a glass transition temperature of 0 ° C to 30 ° C. The separation membrane according to claim 1, wherein the acrylic copolymer has a weight average molecular weight of 10,000 to 1,000,000. The separation membrane according to claim 1, wherein the acrylic monomer is selected from acrylic monomers having a glass transition temperature of 30 占 폚 or lower and an acrylic monomer having a glass transition temperature of 80 占 폚 or higher of the homopolymer. The acrylic pressure-sensitive adhesive composition according to claim 3, wherein the acrylic monomer having a glass transition temperature of 30 ° C or lower is at least one compound selected from the group consisting of n-butyl (meth) acrylate, ethyl (meth) acrylate, (Meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, (Meth) acrylate, and lauryl (meth) acrylate. The separation membrane according to claim 3, wherein the acrylic monomer having a glass transition temperature of 80 ° C or higher is at least one selected from the group consisting of methyl (meth) acrylate, isobonyl (meth) acrylate and cyclohexyl acrylate. The separation membrane according to claim 1, wherein the acrylic monomer containing the furfuryl group comprises the compound of formula (1).
[Chemical Formula 1]

In Formula 1,

Represents a fully saturated, partially unsaturated or fully unsaturated hydrocarbon ring; and R ₁ can be substituted or unsubstituted (CH ₂ ) n, wherein n can be an integer from 1 to 10. The separation membrane according to claim 6, wherein the acrylic monomer containing the furfuryl group is furfuryl (meth) acrylate or tetrahydrofurfuryl (meth) acrylate. The acrylic copolymer according to any one of claims 1 to 7, wherein the acrylic monomer is contained in an amount of 25 to 80% by weight based on the total solid weight of the monomers used for producing the acrylic copolymer, And the acrylic monomer is 5 to 60% by weight. The separation membrane according to claim 1, wherein the acrylic copolymer further contains an acetate group-containing monomer-derived repeating unit. The separation membrane according to any one of claims 1 to 7, wherein the porous adhesive layer further comprises inorganic particles. Porous substrate, and
And a porous adhesive layer formed on one or both surfaces of the porous substrate,
Wherein the porous adhesive layer comprises an acrylic copolymer having a furfuryl group,
Wherein the separator has an anode and an anode adhesive strength of 200 mN / 25 mm or more, respectively. The separator according to claim 11, wherein the separator has an anode adhesive strength of 200 mN / 25 mm to 500 mN / 25 mm and a cathode adhesive strength of the separator is 200 mN / 25 mm to 400 mN / 25 mm. The separator according to claim 11, wherein the adhesive force between the porous adhesive layer and the porous substrate is 700 mN / 25 mm to 1300 mN / 25 mm. The separation membrane according to claim 11, wherein the acrylic copolymer has a glass transition temperature of 0 ° C to 30 ° C. The separation membrane according to claim 11, wherein the acrylic copolymer comprises a first repeating unit derived from an acrylic monomer and a second repeating unit derived from an acrylic monomer containing a furfuryl group. 15. The separation membrane according to claim 14, wherein the acrylic copolymer further contains a repeating unit derived from a vinyl acetate monomer. The separation membrane according to claim 11, wherein the porous adhesive layer further comprises inorganic particles. [15] The method of claim 15, wherein the acrylic monomer is used in an amount of 25 to 80% by weight based on the total solid weight of the monomer used to produce the acrylic copolymer, and the acrylic monomer containing the furfuryl group is 5 to 15% 60 wt%. An electrochemical cell comprising an anode, a cathode, a separator according to any one of claims 1 to 7, and an electrolyte according to any one of claims 1 to 18. The electrochemical cell according to claim 19, wherein the electrochemical cell is a lithium secondary battery.

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