KR20210149491A - A separator for a electrochemical device and a electrochemical device comprising the same - Google Patents

Abstract

The present invention provides a separator for an electrochemical device and an electrochemical device including the same. The device includes: a porous substrate; a heat-resistant layer formed on at least one surface of the porous substrate, and including a heat-resistant polymer and a first binder polymer; and an adhesive layer formed on the surface of the heat-resistant layer and including a second binder polymer, wherein the heat-resistant polymer includes a crystalline heat-resistant polymer having a melting point (T_m) of 250℃ or higher, an amorphous heat-resistant polymer having a glass transition temperature (Tg) of 200℃ or higher, or a combination thereof, a difference between solubility parameters of the first binder polymer and the second binder polymer is 5.0 MPa^(1/2) or less, and the first binder polymer is included in a composition for forming the heat-resistant layer in an amount of 10 to 100 parts by weight based on 100 parts by weight of the heat-resistant polymer. The device has high heat resistance, excellent adhesion, and excellent peel strength between the heat-resistant layer and the adhesive layer.

Description

A separator for an electrochemical device and an electrochemical device having the same

The present invention relates to an electrochemical device having a separator for the electrochemical device. More particularly, it relates to a separator for a battery chemical device having high heat resistance and excellent adhesion, and an electrochemical device having the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and among such secondary batteries, lithium secondary batteries exhibiting high energy density and operating potential, long cycle life, and low self-discharge rate. Batteries have been commercialized and widely used.

This lithium secondary battery is being developed as a model capable of realizing high voltage and high capacity according to the needs of consumers. , and an electrolyte solution optimization process are required.

Among them, the separator is an insulating film that electrically insulates the positive and negative electrodes and is an important component in terms of battery safety. If the secondary battery overheats and thermal runaway occurs or the separator penetrates, there is a high risk of causing an explosion. In particular, the polyolefin-based porous substrate commonly used as a separator of a secondary battery undergoes extreme thermal contraction at a temperature of 100° C. or higher due to material characteristics and characteristics in the manufacturing process including stretching, and as a result, between the positive electrode and the negative electrode cause a short circuit

In order to solve the safety problem of the secondary battery, a separator in which a coating layer using aramid, which is a high heat resistance resin, is formed on at least one surface of a porous polymer substrate having a plurality of pores has been proposed. However, the coating layer using aramid had a problem in that the adhesion between the separator and the electrode was low.

In order to solve the above problems, a separator in which an electrode adhesive layer is formed on the surface of a coating layer having excellent heat resistance has been proposed. However, in this case, there is a problem in that peeling occurs between the coating layer having excellent heat resistance and the electrode adhesive layer.

Accordingly, there is still a very high need for a separator having high heat resistance and excellent adhesion.

Accordingly, the problem to be solved by the present invention is to provide a separator for an electrochemical device having high heat resistance and excellent adhesion, and excellent peel strength between a heat-resistant layer and an adhesive layer, and an electrochemical device having the same.

In addition, another object to be solved by the present invention is to provide a method for manufacturing a separator for an electrochemical device that has high heat resistance and excellent adhesion, and excellent peel strength between a heat-resistant layer and an adhesive layer.

In order to solve the above problems, according to an aspect of the present invention, there is provided a separator for an electrochemical device of the following embodiments.

According to a first embodiment,

porous substrate;

a heat-resistant layer positioned on at least one surface of the porous substrate and including a heat-resistant polymer and a first binder polymer; and

It is located on the surface of the heat-resistant layer, the adhesive layer comprising a second binder polymer; includes,

_{The heat resistant polymer is a crystalline heat resistant polymer having a melting point (melting temperature, T m} ) of 250 ° C. or higher, an amorphous heat resistant polymer having a glass transition temperature (Tg) of 200 ° C. or higher, or a combination thereof,

The difference between the solubility parameter of the first binder polymer and the second binder polymer is 5.0 MPa ^1/2 or less,

The first binder polymer is provided in an amount of 10 to 100 parts by weight based on 100 parts by weight of the heat-resistant polymer, which is included in the heat-resistant layer.

According to a second embodiment, according to the first embodiment,

The second binder polymer may have a melting point of 150° C. or less.

According to a third embodiment, according to the first or second embodiment,

The heat-resistant polymer is polyacetal, polysulfone (PSF), polyethersulfone (PES), polyetherimide (PEI), polyphenylenesulfide (PPS), polyetheretherketone (PEEK), polyarylate (PA) , polycarbonate, polyamideimide (PAI), polyimide (PI), polyamide, wholly aromatic polyamide (aramid), polyphenylene oxide, polybutylene terephthalate, polyethylene terephthalate, polyether ketone, or any of these It may include two or more.

According to a fourth embodiment, according to the second or third embodiment,

The second binder polymer is polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-tetrafluoroethylene, polyvinylidene fluoride- co-trifluoroethylene, polyvinylidene fluoride-co-trifluorochloroethylene, polyvinylidene fluoride-co-ethylene, or two or more of these.

According to a fifth embodiment, according to any one of the first to fourth embodiments,

The heat-resistant layer may further include inorganic particles.

According to a sixth embodiment, according to any one of the first to fifth embodiments,

The adhesive layer may further include inorganic particles.

In order to solve the above problems, according to an aspect of the present invention, there is provided a method of manufacturing a separator for an electrochemical device of the following embodiments.

According to a seventh embodiment,

Preparing a porous substrate (S1);

Preparing a composition for forming a heat-resistant layer comprising a heat-resistant polymer, a first binder polymer, and a first solvent (S2);

forming a heat-resistant layer by coating the composition for forming a heat-resistant layer on at least one surface of the porous substrate (S3); and

and coating a composition for forming an adhesive layer comprising a second binder polymer and the second solvent on the surface of the heat-resistant layer to form an adhesive layer (S4);

_{The heat resistant polymer is a crystalline heat resistant polymer having a melting point (melting temperature, T m} ) of 250 ° C. or higher, an amorphous heat resistant polymer having a glass transition temperature (Tg) of 200 ° C. or higher, or a combination thereof,

The difference between the solubility parameter of the first binder polymer and the second binder polymer is 5.0 MPa ^1/2 or less,

The first binder polymer is provided in an amount of 10 to 100 parts by weight based on 100 parts by weight of the heat-resistant polymer, which is included in the composition for forming a heat-resistant layer.

According to the eighth embodiment, according to the seventh embodiment,

The first binder polymer may have a solubility of 5 wt% or more at 25 °C with respect to the first solvent.

According to a ninth embodiment, according to the seventh or eighth embodiment,

After the step (S3) of forming the heat-resistant layer is coated with a composition for forming a heat-resistant layer comprising the heat-resistant polymer, the first binder polymer, and the first solvent on at least one surface of the porous substrate, the first non-solvent It may include the step of phase separation by immersion in a coagulation solution containing a.

According to a tenth embodiment, according to any one of the seventh to ninth embodiments,

In the step (S4) of forming the adhesive layer, the composition for forming an adhesive layer including the second binder polymer and the second solvent is coated on the surface of the heat-resistant layer, and then immersed in a coagulating solution containing a second non-solvent. It may include a step of phase separation.

According to an eleventh embodiment, according to any one of the seventh to ninth embodiments,

After the step of forming the adhesive layer (S4) is coated with the composition for forming an adhesive layer comprising the second binder polymer and the second solvent on the surface of the heat-resistant layer, phase separation under a second non-solvent atmosphere in the gas phase may include

According to the twelfth embodiment, according to the tenth or eleventh embodiment,

The first binder polymer may have a solubility of 10% by weight or less at 25°C in the second solvent, and may have a solubility of 2% by weight or less at 25°C in the second non-solvent.

According to the thirteenth embodiment, according to the eleventh embodiment,

When the second non-solvent is water,

After the step of forming the adhesive layer (S4) is coated with the composition for forming an adhesive layer comprising the second binder polymer and the second solvent on the surface of the heat-resistant layer, humidifying phase separation under a condition of 40 to 80% relative humidity. may include

In order to solve the above problems, according to an aspect of the present invention, an electrochemical device of the following embodiments is provided.

According to a fourteenth embodiment,

An electrochemical device comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the separator is the separator of any one of claims 1 to 6 is provided.

The separator for an electrochemical device of the present invention includes a heat-resistant layer and an adhesive layer, and thus has high heat resistance and excellent adhesion.

In addition, the separator for an electrochemical device of the present invention has excellent peel strength between the heat-resistant layer and the adhesive layer and has high interfacial adhesion by including a compatible binder polymer in the heat-resistant layer with a small difference in solubility index from the binder polymer of the adhesive layer.

The following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the above-described content of the present invention, so the present invention is limited to the matters described in those drawings It should not be construed as being limited.
1 schematically shows a cross section of a separator according to an embodiment of the present invention.
2 is a schematic cross-section of a separator according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

Accordingly, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiment of the present invention and do not represent all the technical spirit of the present invention, so at the time of the present application, various It should be understood that there may be equivalents and variations.

In this specification, terms such as “first” and “second” are used to distinguish one component from other components, and each component is not limited by the terms.

The separator for an electrochemical device of the present invention includes a porous substrate;

a heat-resistant layer positioned on at least one surface of the porous substrate and including a heat-resistant polymer and a first binder polymer; and

It is located on the surface of the heat-resistant layer, the adhesive layer comprising a second binder polymer; includes,

The heat resistant polymer is a crystalline heat resistant polymer having a melting point (melting temperature, T _m ) of 250 ° C. or higher, or an amorphous heat resistant polymer having a glass transition temperature (Tg) of 200 ° C. or higher, or a combination thereof,

The difference between the solubility parameter of the first binder polymer and the second binder polymer is 5.0 MPa ^1/2 or less,

The first binder polymer is included in the heat-resistant layer in an amount of 10 to 100 parts by weight based on 100 parts by weight of the heat-resistant polymer.

1 shows a cross-section of a separator 1 according to an embodiment of the present invention. Referring to this, the separator 1 includes a porous substrate 100 and a heat-resistant layer 110 positioned on one surface of the porous substrate 100 . In addition, an adhesive layer 120 is provided on the surface of the heat-resistant layer 110 .

2 shows a cross-section of a separator 2 according to another embodiment of the present invention. The separator 2 includes a porous substrate 200 and heat-resistant layers 210 positioned on both sides of the porous substrate 100 . In addition, an adhesive layer 220 is provided on the surface of the heat-resistant layer 210 .

In one embodiment of the present invention, the porous substrate can be used without any particular limitation as long as it can be used as a material for a separator for an electrochemical device in general. The porous substrate is a thin film containing a polymer material, and non-limiting examples of the polymer material include polyolefin resin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether. It may include at least one of a polymer resin such as ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene. In addition, the porous substrate may be a nonwoven fabric or a porous polymer film formed of the polymer material as described above, or a laminate of two or more thereof. Specifically, the porous substrate is any one of the following a) to e).

a) a porous film formed by melting and extruding a polymer resin;

b) a multilayer film in which two or more layers of the porous film of a) are laminated;

c) a nonwoven web prepared by integrating filaments obtained by melting/spinning a polymer resin;

d) a multilayer film in which two or more layers of the nonwoven web of b) are laminated;

e) A porous composite membrane having a multilayer structure comprising at least two of a) to d).

In one embodiment of the present invention, the thickness of the porous substrate may be 5 μm to 50 μm. Although the thickness range of the porous substrate is not particularly limited to the above-mentioned range, when the thickness is excessively thinner than the above-mentioned lower limit, mechanical properties are deteriorated, and the separator may be easily damaged during battery use. Meanwhile, the pore size and pore size present in the porous substrate are also not particularly limited, but may be 0.01 μm to 50 μm and 10% to 95%, respectively.

On the other hand, in the present invention, the porosity and pore size is a scanning electron microscope (SEM) image, a mercury porosimeter (Mercury porosimeter), capillary flow porometer (capillary flow porometer) or pore distribution analyzer (Porosimetry analyzer; Bell Japan) Inc, Belsorp-II mini) can be used to measure the BET 6-point method by nitrogen gas adsorption flow method, but a capillary flow pore distribution analyzer is most suitable.

The separator for an electrochemical device according to the present invention is provided with a heat-resistant layer including a heat-resistant polymer and a first binder polymer. The heat resistant polymer is a crystalline heat resistant polymer having a melting point of 250° C. or higher, an amorphous heat resistant polymer having a glass transition temperature of 200° C. or higher, or a combination thereof. Accordingly, the surface of the porous substrate is coated with a heat-resistant polymer, thereby improving the heat resistance and mechanical properties of the porous substrate.

In particular, compared to crystalline heat-resistant polymers whose mechanical rigidity drops sharply above the melting point, amorphous heat-resistant polymers do not have a melting point and have the property of maintaining mechanical rigidity even at temperatures above the glass transition temperature, which is more advantageous in securing separator safety.

The separator for an electrochemical device according to the present invention has excellent peel strength between the adhesive layer and the heat-resistant layer by including the first binder polymer in the heat-resistant layer, thereby preventing the adhesive layer and the heat-resistant layer from being peeled off.

In order to prevent peeling between the adhesive layer and the heat-resistant layer, the first binder polymer has a solubility parameter of 5.0 MPa ^1/2 or less with a second binder polymer to be described later. In the present invention, the difference in solubility index between the first binder polymer and the second binder polymer is a numerical value representing the affinity between the first binder polymer and the second binder polymer. The difference in solubility index between the first binder polymer and the second binder polymer may be generally calculated using a Hansen solubility parameter.

The Hansen Solubility Parameter (HSP) was proposed by Dr.C.Hansen in 1967 and is known to most accurately represent solubility characteristics. In HSP, the degree of binding within a substance is considered by subdividing it into the following three factors.

(1) solubility factor (δD) due to nonpolar dispersion bonding

(2) Solubility factor (δP) due to polar bonding due to permanent dipole

(3) solubility factor (δH) resulting from hydrogen bonding

As such, HSP is widely used because it provides more detailed information about the binding in a substance than other solubility factors, so it can evaluate the solubility or miscibility of a substance more accurately and systematically.

HSP=(δD, δP, δH), MPa ^½ (1)

^{δTot = (δD 2 + δP 2} + δH 2) ½, MPa ½ (2)

HSP is a vector having magnitude and direction in a space consisting of three elements, and δTot represents the magnitude of the HSP vector. The basic unit for HSP is MPa ^½ . These HSP values are calculated using a program called HSPiP (Hansen Solubility Parameters in Practice) developed by the Dr.Hansen group that proposed HSP. As mentioned above, if the HSP values of two substances are similar, they dissolve well. Since HSP is a vector, in order to judge that they are similar, the three HSP components of each substance and the size of the HSP must all be similar. All substances have HSP and can be used to predict whether or not substances of interest will dissolve in each other through comparative analysis of differences in similarity.

Specifically, the first binder polymer may have a solubility parameter difference between the second binder polymer and the second binder polymer of 5.0 MPa ^1/2 or less, 3.5 MPa ^1/2 or less, or 0.1 to 2.5 MPa ^1/2 or less. When the difference in solubility index between the first binder polymer and the second binder polymer is within the above range, there is compatibility with the second binder polymer used in the adhesive layer. In the separator for an electrochemical device according to the present invention, the heat resistance The layer and the adhesive layer can be prevented from peeling off each other.

In the present invention, compatibility means the chemical affinity of the first binder polymer and the second binder polymer.

In one embodiment of the present invention, the first binder polymer may be included in the heat-resistant layer in an amount of 10 parts by weight or more, 30 parts by weight or more, or 50 to 100 parts by weight based on 100 parts by weight of the heat-resistant polymer. When the first binder polymer is included in the heat-resistant layer in the above-described range with respect to 100 parts by weight of the heat-resistant polymer, compatibility between the heat-resistant layer and the adhesive layer is further improved, so that the adhesive strength between the adhesive layer and the heat-resistant layer is further improved while securing heat-resistant properties can be easy to do. That is, the peel strength between the adhesive layer and the heat-resistant layer may be greater.

In the present invention, the heat-resistant polymer is a crystalline polymer resin having a high melting point of 250 °C or higher, an amorphous polymer resin having a glass transition temperature of 200 °C or higher, or a combination thereof. Non-limiting examples of such heat-resistant polymers include polyacetal, polysulfone (PSF), polyethersulfone (PES), polyetherimide (PEI), polyphenylenesulfide (PPS), polyetheretherketone (PEEK), polyarylay PA, polycarbonate, polyamideimide (PAI), polyimide (PI), polyamide, wholly aromatic polyamide (aramid), polyphenylene oxide, polybutylene terephthalate, polyethylene terephthalate, polyether ketone , or two or more of them. In one embodiment of the present invention, the heat-resistant polymer may include at least one of polyamide and wholly aromatic polyamide. Further, in a specific embodiment of the present invention, the wholly aromatic polyamide refers to a polymer having an amide bond directly attached between two aromatic rings of 85% or more. The wholly aromatic polyamide may be classified into a para-type wholly aromatic polyamide and a meta-type wholly aromatic polyamide according to the position of the amide bond bonded to the aromatic ring.

In one embodiment of the present invention, non-limiting examples of the first binder polymer include polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene , polyvinylidene fluoride-co-tetrafluoroethylene, polyvinylidene fluoride-co-trifluoroethylene, polyvinylidene fluoride-co-trifluorochloroethylene and polyvinylidene fluoride-co-ethylene , or two or more of them.

In the present invention, the heat-resistant layer 110 is located on one side or both sides of the porous substrate.

In one embodiment of the present invention, the heat-resistant layer may have a thickness in the range of 1.0 μm to 10.0 μm. The heat-resistant layer may have an appropriate thickness within the above range, for example, the thickness may be 1.5 μm to 8.0 μm, 2.0 μm to 6.0 μm, or 2.5 μm to 5.0 μm. When the thickness of the heat-resistant layer satisfies the above range, it is effective to prevent thermal shrinkage of the separator and may exhibit a desired level of mechanical properties such as improvement in penetration strength. In one embodiment of the present invention, the pore size and porosity of the heat-resistant layer may be 0.001 to 1.0 μm, respectively, and may be appropriately adjusted in the range of 30 to 80%.

In addition, in the separator for an electrochemical device of the present invention, an adhesive layer including a second binder polymer having adhesiveness is formed on the surface of the heat-resistant layer, so that the separator has excellent adhesion to the electrode.

In one embodiment of the present invention, the second binder polymer refers to a polymer resin capable of implementing adhesion between the electrode and the separator. In one embodiment of the present invention, the second binder polymer may have a melting point of 150 ℃ or less. Non-limiting examples of the second binder polymer having a melting point of 150° C. or less include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co -tetrafluoroethylene, polyvinylidene fluoride-co-trifluoroethylene, polyvinylidene fluoride-co-trifluorochloroethylene, polyvinylidene fluoride-co-ethylene, or two or more thereof can do.

Also in one embodiment of the present invention, the second binder polymer is 200,000 to 450,000, or 250,000 to 350,000 may have a weight average molecular weight. When the second binder polymer has a weight average molecular weight within the above-described range, when pressure is applied in the process of assembling the electrode assembly, the second binder polymer may be easily deformed and adhesive properties with the electrode may be improved.

The weight average molecular weight was measured by gel permeation chromatography (GPC, PL GPC220, Agilent Technologies) under the following conditions.

- Column: PL Olexis (Polymer Laboratories)

- Solvent: TCB (Trichlorobenzene)

- Flow rate: 1.0 ml/min

- Sample concentration: 1.0 mg/ml

- Injection volume: 200 μl

- Column temperature: 160℃

- Detector: Agilent High Temperature RI detector

- Standard: Polystyrene (corrected by cubic function)

In one embodiment of the present invention, the adhesive layer may have a thickness in the range of 0.2 μm to 2.0 μm on one surface of the porous substrate. The adhesive layer may have an appropriate thickness within the above range, for example, the thickness may be 0.3 μm to 1.8 μm, or 0.5 μm to 1.5 μm. When the thickness of the adhesive layer satisfies the above range, it may exhibit a desired level of adhesion to the electrode. In one embodiment of the present invention, the pore size and porosity of the adhesive layer may be 0.001 to 1.0 μm, respectively, and may be appropriately adjusted in the range of 30 to 80%.

In one embodiment of the present invention, the heat-resistant layer may further include inorganic particles. In one embodiment of the present invention, when the heat-resistant layer further includes inorganic particles, the content of the inorganic particles may be 10 to 250 parts by weight when the total content of the heat-resistant polymer and the first binder polymer is 100 parts by weight. When the inorganic particles are included in the above-described range based on the total content of the heat-resistant polymer and the first binder polymer, the pore-forming accelerating effect and resistance property improvement can be ensured, and the heat-resistant polymer can guarantee heat-resistance properties. may be included.

In one embodiment of the present invention, the adhesive layer may further include inorganic particles. In one embodiment of the present invention, when the adhesive layer further includes inorganic particles, the content of the inorganic particles may be 10 to 250 parts by weight when the total content of the second binder polymer included in the adhesive layer is 100 parts by weight. When the inorganic particles are included in the above-described range based on the content of the second binder polymer, the pore formation promoting effect and resistance property improvement can be ensured, and the second binder polymer can ensure the adhesion between the electrode and the separator. can be included as

In a specific embodiment of the present invention, the inorganic particles preferably have properties that do not change their physical properties even under high temperature conditions of 200° C. or higher. In addition, the inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles are not particularly limited as long as oxidation and/or reduction reactions do not occur in the operating voltage range of the applied electrochemical device (eg, 0-5V based on Li/Li+). In a specific embodiment of the present invention, the inorganic particles include, for example, BaTiO ₃ , BaSO ₄ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-x La _x Z _r1-y Ti _y O ₃ (PLZT, where 0 < x < 1, 0 < y < 1), Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), Hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgOH ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , AlOOH, Al(OH) ₃ , SiC, TiO ₂ , or two or more of these may include

In a specific embodiment of the present invention, the inorganic particle size is not particularly limited. The size of the inorganic particles may be in the range of about 0.001 μm to 3 μm in diameter in consideration of the formation of a heat-resistant layer and/or an adhesive layer having a uniform thickness and an appropriate porosity. When the inorganic particle size satisfies the above range, dispersibility is maintained, so it is easy to control the physical properties of the separator, and the increase in the thickness of the heat-resistant layer and/or the adhesive layer can be avoided, so that mechanical properties can be improved, In addition, due to the excessively large pore size, the probability of an internal short circuit occurring during battery charging and discharging is low. In one embodiment of the present invention, the inorganic particles may be appropriately adjusted in consideration of porosity and pore size within the above range. For example, the diameter may be 3 μm or less, 2.5 μm or less, 2.0 μm or less, 1.5 μm or less, 1 μm or less, or 500 nm or less within the above range, and 10 nm or more, 20 nm or more, 30 nm or more, 50 nm or less. or more, 80 nm or more, 100 nm or more, or 150 nm or more may be appropriately adjusted.

Next, a method for manufacturing a separator according to the present invention will be described.

A method of manufacturing a separator according to the present invention includes the steps of preparing a porous substrate (S1);

Preparing a composition for forming a heat-resistant layer comprising a heat-resistant polymer, a first binder polymer, and a first solvent (S2);

forming a heat-resistant layer by coating the composition for forming a heat-resistant layer on at least one surface of the porous substrate (S3); and

and coating a composition for forming an adhesive layer comprising a second binder polymer and a second solvent on the surface of the heat-resistant layer to form an adhesive layer (S4).

In this case, the heat resistant polymer is a _{crystalline heat resistant polymer having a melting point (melting temperature, T m} ) of 250 ° C. or higher, an amorphous heat resistant polymer having a glass transition temperature (Tg) of 200 ° C. or higher, or a combination thereof,

The difference between the solubility parameter of the first binder polymer and the second binder polymer is 5.0 MPa ^1/2 or less,

The first binder polymer is included in the composition for forming the heat-resistant layer in an amount of 10 to 100 parts by weight based on 100 parts by weight of the heat-resistant polymer.

Hereinafter, the above steps will be described in more detail.

First, a porous substrate is prepared (S1).

For the porous substrate, refer to the above description.

Next, a heat-resistant polymer and a first binder polymer are dissolved in a first solvent to prepare a composition for forming a heat-resistant layer (S2). For the heat-resistant polymer, refer to the above description. For the first binder polymer, refer to the above description. The first solvent means a solvent for the heat-resistant polymer. The first solvent preferably has a solubility index similar to that of the heat-resistant polymer to be used, and is miscible with a non-solvent for phase separation. This is to facilitate the uniform mixing of the heat-resistant polymer and the solvent removal in the subsequent drying step. Non-limiting examples of the solvent that can be used include tetrahydrofuran, methylene chloride, chloroform, acetone, methylethylketone, dimethylacetamide, dimethylformamide. (dimethylformamide), N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP), cyclohexane, or two or more thereof.

In one embodiment of the present invention, the first binder polymer may have a solubility of 5 wt% or more at 25 °C with respect to the first solvent. Specifically, the first binder polymer may have a solubility in the first solvent of 5 wt% or more, 7 wt% or more, or 8 to 35 wt% at 25°C. When the first binder polymer has a solubility in the above-mentioned range with respect to the first solvent, the first binder polymer is well dissolved in the composition for forming a heat-resistant layer, so that it is easy to form a heat-resistant layer together with the heat-resistant polymer.

The first binder polymer may be included in the composition for forming the heat-resistant layer in an amount of 10 parts by weight or more based on 100 parts by weight of the heat-resistant polymer. Specifically, the first binder polymer may be included in the composition for forming a heat-resistant layer in an amount of 10 parts by weight or more, 20 parts by weight or more, or 30 to 100 parts by weight based on 100 parts by weight of the heat-resistant polymer. When the first binder polymer is included in the composition for forming a heat-resistant layer within the above-mentioned range, the first binder is included in the heat-resistant layer in a sufficient amount to make it easier to improve the adhesive force between the adhesive layer and the heat-resistant layer and to secure heat resistance properties can do.

The composition for forming the heat-resistant layer may optionally include inorganic particles. For the inorganic particles, refer to the above description. When inorganic particles are included in the composition for forming the heat-resistant layer, the composition for forming the heat-resistant layer may be in the form of a slurry. In this case, in order to add the inorganic particles to the composition for forming a heat-resistant layer, the step of adding and dispersing the inorganic particles may be additionally performed. Further, in one embodiment of the present invention, after the inorganic particles are added to the composition for forming a heat-resistant layer, crushing of the inorganic particles may be performed. In this case, the crushing time is appropriate for 1 to 20 hours, and the size of the crushed inorganic particles is the same as described above. As the crushing method, a conventional method may be used, for example, a ball mill method is preferable.

When inorganic particles are further included in the composition for forming a heat-resistant layer including the heat-resistant polymer and the first binder polymer, the total content of the heat-resistant polymer and the first binder polymer and the composition ratio of the inorganic particles are not significantly restricted, but according to the It can be appropriately adjusted according to the thickness, pore size and porosity of the heat-resistant layer of the present invention. In particular, when the total content of the heat-resistant polymer and the first binder polymer is 100 parts by weight, 10 to 250 parts by weight of inorganic particles may be included. When the inorganic particles are included in the above-described range based on the total content of the heat-resistant polymer and the first binder polymer, the pore-forming accelerating effect and resistance property improvement can be ensured, and the heat-resistant polymer can guarantee heat-resistance properties. may be included.

Next, the prepared composition for forming a heat-resistant layer is coated on at least one surface of the porous substrate to form a heat-resistant layer (S3).

A method of coating the composition for forming the heat-resistant layer on the porous substrate may use a conventional coating method known in the art, for example, dip coating, die coating, roll coating, comma Various methods such as (comma) coating or a mixture thereof may be used.

In a specific embodiment of the present invention, in the step (S3) of forming the heat-resistant layer, a composition for forming a heat-resistant layer comprising the heat-resistant polymer, the first binder polymer, and the first solvent is applied to at least one surface of the porous substrate. After coating, it may include the step of phase separation by immersing in a coagulation solution containing the first non-solvent.

The first non-solvent refers to a non-solvent for the heat-resistant polymer and the first binder polymer.

Specifically, the step of phase separation by immersion will be described as follows.

The composition for forming a heat-resistant layer is coated on at least one surface of the porous substrate, and the composition is immersed in a coagulating solution containing the first non-solvent for a predetermined time. Accordingly, as the first solvent in the composition for forming the heat-resistant layer in the coagulating solution is replaced with the first non-solvent, phase separation in the composition for forming the heat-resistant layer proceeds to solidify the heat-resistant polymer and the first binder polymer. In this process, the heat-resistant layer including the heat-resistant polymer and the first binder polymer is made porous. Thereafter, all of the first solvent remaining in the composition for forming a heat-resistant layer is replaced with the first non-solvent by washing with a pure first non-solvent, and the heat-resistant layer is applied to at least one surface of the porous substrate by removing the first non-solvent from the drying furnace. can be formed

In one embodiment of the present invention, the non-solvent is alcohols such as methyl alcohol (methanol), ethyl alcohol (ethanol), isopropyl alcohol (IPA), propyl alcohol (propanol), butyl alcohol (butanol), water, or It may be two or more of these, but is not necessarily limited thereto, and any nonsolvent or poor solvent that can be used in the art may be used.

As the coagulating solution, only the first non-solvent or a mixed solvent of the first non-solvent and the first solvent as described above may be used. When a mixed solvent of the first non-solvent and the first solvent is used, the content of the first non-solvent may be 60 wt % or more relative to 100 wt % of the coagulating solution from the viewpoint of forming a good porous structure and improving productivity .

In one embodiment of the present invention, the first non-solvent included in the coagulating solution may be included in an amount of 100 to 800 parts by weight, 150 to 600 parts by weight, or 200 to 500 parts by weight based on 100 parts by weight of the first solvent. When the range of the first non-solvent is within the above range, it is easy to form pores by phase separation in the composition for forming a heat-resistant layer, and it is possible to prevent the problem that the heat-resistant layer is not dense and microvoids are formed due to excessive phase separation. can

Next, an adhesive layer is formed by coating the surface of the heat-resistant layer with a composition for forming an adhesive layer including a second binder polymer and a second solvent (S4).

For the second binder polymer, refer to the above description. The second solvent means a solvent for the second binder polymer. The second solvent preferably has a solubility index similar to that of the second binder polymer to be used in the adhesive layer and has a low boiling point. This is to facilitate uniform mixing and subsequent solvent removal. Non-limiting examples of the solvent that can be used include acetone, tetrahydrofuran, methylene chloride, chloroform, acetone, methylethylketone, dimethylacetamide ), dimethylformamide (dimethylformamide), N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP), cyclohexane, or two or more thereof. In one embodiment of the present invention, the content of the second binder polymer in the composition for forming an adhesive layer may be 1 wt% to 10 wt%.

The composition for forming the adhesive layer may optionally include inorganic particles. For the inorganic particles, refer to the above description. When inorganic particles are included in the composition for forming the adhesive layer, the composition for forming the adhesive layer may be in the form of a slurry. In this case, in order to add the inorganic particles to the composition for forming an adhesive layer, the step of adding and dispersing the inorganic particles may be additionally performed. Further, in one embodiment of the present invention, after adding the inorganic particles to the composition for forming an adhesive layer, crushing of the inorganic particles may be performed. In this case, the crushing time is appropriate for 1 to 20 hours, and the size of the crushed inorganic particles is the same as described above. As the crushing method, a conventional method may be used, for example, a ball mill method is preferable.

When inorganic particles are further included in the composition for forming an adhesive layer containing the second binder polymer, the total content of the second binder polymer and the composition ratio of the inorganic particles are not significantly limited, but the thickness of the adhesive layer of the present invention finally manufactured according to this, It can be appropriately adjusted according to the pore size and porosity. In particular, when the content of the second binder polymer is 100 parts by weight, 10 to 250 parts by weight of inorganic particles may be included. When the inorganic particles are included in the above-described range based on the content of the second binder polymer, the pore formation promoting effect and resistance can be ensured, and the second binder polymer is included to the extent that it can guarantee the adhesion between the electrode and the separator. can

In one embodiment of the present invention, after the step of forming the adhesive layer (S4) is coated with a composition for forming an adhesive layer comprising the second binder polymer and the second solvent on the surface of the heat-resistant layer, the second cost It may include the step of phase separation by immersion in a coagulation solution containing a medium.

In the present invention, the second non-solvent means a non-solvent for the second binder polymer.

Specifically, the step of phase separation by immersion will be described as follows.

A composition for forming an adhesive layer is coated on the surface of the heat-resistant layer and immersed in a coagulating solution containing a second non-solvent for a predetermined time. Accordingly, as the second solvent in the composition for forming an adhesive layer in the coagulating solution is replaced with the second non-solvent, phase separation in the composition for forming an adhesive layer proceeds to solidify the second binder polymer. In this process, the adhesive layer including the second binder polymer is made porous. Thereafter, by washing with a pure second non-solvent, the second solvent remaining in the composition for forming an adhesive layer is all replaced with the second non-solvent, and an adhesive layer can be formed on the surface of the heat-resistant layer by removing the second non-solvent from the drying furnace. have.

In one embodiment of the present invention, the second non-solvent is water, methanol, ethanol, isopropanol, propylalcohol, butylalcohol, butylalcohol, butanediol , ethylene glycol, propylene glycol, or two or more of these, but is not necessarily limited thereto, and any nonsolvent or poor solvent that can be used in the art may be used.

As the coagulating solution, only the second non-solvent or a mixed solvent of the second non-solvent and the second solvent as described above may be used. When a mixed solvent of the second non-solvent and the second solvent is used, the content of the second non-solvent may be 60 wt % or more relative to 100 wt % of the coagulating solution from the viewpoint of forming a good porous structure and improving productivity .

In one embodiment of the present invention, the second non-solvent included in the coagulating solution may be included in an amount of 200 to 1500 parts by weight, 250 to 1200 parts by weight, or 300 to 1000 parts by weight based on 100 parts by weight of the second solvent. When the range of the second non-solvent is within the above-mentioned range, it is easy to form pores due to phase separation in the composition for forming an adhesive layer, and to control the thickness of the adhesive layer.

In another embodiment of the present invention, after the step (S4) of forming the adhesive layer is coated with a composition for forming an adhesive layer comprising the second binder polymer and the second solvent on the surface of the heat-resistant layer, the 2 It may include the step of phase separation in a non-solvent atmosphere.

In one embodiment of the present invention, the second nonsolvent may be introduced in a gaseous state for phase separation. The second non-solvent is not particularly limited as long as it does not dissolve the second binder polymer and has partial compatibility with the second solvent, and specifically, the second non-solvent is water, methanol, It may be ethanol, isopropanol, propylalcohol, butylalcohol, butandiol, ethylene glycol, propylene glycol, or two or more of these.

When the second non-solvent is introduced and added in a gaseous state, it is possible to phase-separate using a small amount of the non-solvent, and there is an advantage in that the composition for forming an adhesive layer is more easily dried.

At this time, the temperature at which the second non-solvent is added in a gaseous state may be in the range of 15 ° C to 70 ° C. Productivity is low, and when the temperature is higher than 70° C., the drying rate of the second solvent and the second non-solvent is too fast, so that it is difficult to sufficiently separate the phases.

In one embodiment of the present invention, when the second non-solvent is water, the step of forming the adhesive layer (S4) is coated with a composition for forming an adhesive layer comprising the second binder polymer and a second solvent on the surface of the heat-resistant layer. After that, it may include a step of humidifying the phase separation under the conditions of 40 to 80% relative humidity.

Specifically, the humidifying phase separation step will be described as follows.

The humidifying phase separation may include drying the composition for forming an adhesive layer under a condition of 40% to 80% relative humidity. When the second solvent in the composition for forming an adhesive layer moves to the surface portion of the coated composition and is removed by drying by drying under humidification treatment conditions, the second binder polymer moves to the surface portion of the coated composition together with the second solvent and finally obtained It may be concentrated on the upper layer of the adhesive layer.

In one embodiment of the present invention, the relative humidity is preferably controlled to 80% or less, or 75% or less, or 40 to 70% in consideration of the pore formation and resistance properties of the adhesive layer. When the vapor pressure of the non-solvent satisfies this range, the problem of difficulty in obtaining a uniform coating because the amount of the non-solvent is too small to sufficiently cause phase separation or because the phase separation occurs too much can be prevented.

In one embodiment of the present invention, the first binder polymer may have a solubility of 10 wt% or less at 25 °C with respect to the second solvent. Specifically, the solubility of the first binder polymer in the second solvent may be 10 wt% or less, 8 wt% or less, or 0.1 to 5 wt% at 25°C. When the first binder polymer has a solubility in the above-described range with respect to the second solvent, after the heat-resistant layer including the first binder polymer is formed, the composition for forming an adhesive layer in the process of forming an adhesive layer on the surface of the heat-resistant layer Since the first binder polymer is not dissolved in the second solvent contained in the , it may remain in the heat-resistant layer. Accordingly, in the finally manufactured separator, the first binder polymer may increase the adhesion between the heat-resistant layer and the adhesive layer.

Further, in one embodiment of the present invention, the first binder polymer may have a solubility of 2 wt% or less at 25 °C with respect to the second non-solvent. Specifically, the solubility of the first binder polymer with respect to the second non-solvent may be 2 wt% or less, 1 wt% or less, or 0.1 to 1 wt% at 25°C. When the first binder polymer has solubility in the above-described range with respect to the second non-solvent, after the heat-resistant layer including the first binder polymer is formed, when the phase separation step of the adhesive layer occurs, the first binder in the second non-solvent The polymer may not dissolve and remain in the heat-resistant layer. Accordingly, in the finally manufactured separator, the first binder polymer may increase the adhesion between the heat-resistant layer and the adhesive layer.

The separator for an electrochemical device of the present invention may be manufactured as an electrochemical device by being interposed between the positive electrode and the negative electrode.

The electrochemical device of the present invention includes all devices that undergo an electrochemical reaction, and specific examples thereof include all kinds of primary, secondary cells, fuel cells, solar cells, or capacitors such as supercapacitor devices. . In particular, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery among the secondary batteries is preferable.

The electrode to be applied together with the separator for a lithium secondary battery of the present invention is not particularly limited, and the electrode active material may be prepared in a form bound to the current collector according to a conventional method known in the art.

Among the electrode active materials, non-limiting examples of the positive electrode active material include conventional positive electrode active materials that can be used in positive electrodes of conventional electrochemical devices, and in particular, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof. It is preferable to use one lithium composite oxide.

As a non-limiting example of the negative electrode active material, a conventional negative electrode active material that can be used for the negative electrode of a conventional electrochemical device can be used, and in particular, lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, A lithium adsorbent material such as graphite or other carbons is preferable. Non-limiting examples of the positive current collector include a foil made of aluminum, nickel, or a combination thereof, and non-limiting examples of the negative current collector include copper, gold, nickel, or a copper alloy or a combination thereof. There are manufactured foils and the like.

According to a specific embodiment of the present invention, the electrolyte that can be used in an electrochemical device is a salt having the same structure as ^{A +} B ^{-, and A +} is Li ⁺ , Na ⁺ , K ⁺ such as alkali metal cations or a combination thereof. and B ^- is PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- ,I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N(CF ₃ SO ₂ ) ₂ ^- , C(CF ₂ SO ₂ ) ₃ ^- A salt containing an anion such as or a combination thereof is propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl Carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC) , gamma-butyrolactone (γ-butyrolactone) or dissolved or dissociated in an organic solvent consisting of a mixture thereof, but is not limited thereto.

The electrolyte injection may be performed at an appropriate stage during the battery manufacturing process according to the manufacturing process and required physical properties of the final product. That is, it may be applied before assembling the battery or in the final stage of assembling the battery.

According to a specific embodiment of the present invention, as a process for applying the separator for a lithium secondary battery to a battery, in addition to the general process of winding, lamination, stack, and folding processes of the separator and the electrode are possible. .

According to a specific embodiment of the present invention, the separator for a lithium secondary battery may be interposed between the positive electrode and the negative electrode of the secondary battery, and when a plurality of cells or electrodes are assembled to form an electrode assembly, between adjacent cells or electrodes may be interposed. The electrode assembly may have various structures such as a simple stack type, a jelly-roll type, a stack-folding type, and a lamination-stack type.

Hereinafter, test examples and examples will be described in detail to help the understanding of the present invention. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the following examples. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

Example 1

20 parts by weight of polyetherimide (PEI) resin (Sabic Ultem 1000, glass transition temperature 217° C.) as a heat-resistant polymer in N-methyl-2-pyrrolidone (NMP) and PVdF-HFP resin (Arkema) as the first binder polymer LBG, melting point 152° C., weight average molecular weight 740,000) was added and dissolved, and then alumina (Al ₂ O ₃ , Sumitomo AES11) was added to 100 parts by weight based on the total of 100 parts by weight of the heat-resistant polymer and the first binder polymer. A composition for forming a heat-resistant layer was prepared by adding and dispersing parts by weight. A polyethylene film (Senior SW310H, ventilation time 90 sec/100 cc) was used as a porous substrate, and the composition for forming a heat-resistant layer was coated on both sides on the porous substrate by a dip coating method, and then water and NMP were 80: The phase was separated by immersion again in the coagulation bath composed of 20. The total thickness of the preliminary separator provided with heat-resistant layers on both surfaces of the porous substrate thus obtained was 14 μm, and the ventilation time was 148 sec/100 cc.

Subsequently, adhesive layers were formed on both surfaces of the preliminary separator. As the second binder polymer, 5 parts by weight of PVdF-HFP resin (Solvay's Solef21510, melting point 135°C, weight average molecular weight 280,000) was added to acetone to prepare a composition for forming an adhesive layer. The composition for forming an adhesive layer was coated on both sides of the separator by a dip coating method using the composition for forming an adhesive layer prepared in this way, and it was dried under a condition controlled at a humidity of 55% to 65% to obtain a separator with an adhesive layer did In the separator, the adhesive layer had a thickness of about 0.5 μm on each side and a total thickness of 1 μm on both sides, the total thickness of the separator was 15 μm, and the ventilation time was 192 sec/100 cc.

The solubility parameter of the first binder polymer and the second binder polymer was measured using the above-described method. δD, δP, and δH values of the first binder polymer were 17.2, 12.5, and 8.2, respectively. δD, δP, and δH values of the second binder polymer were 17.2, 12.5, and 8.2, respectively.

At this time, the difference in solubility parameter between the first binder polymer and the second binder polymer was 0.0 MPa ^1/2 .

Example 2

A separator was prepared in the same manner as in Example 1, except that PVdF-TFE resin (VT475 by Daikin, melting point 132° C.) was used as the first binder polymer. The total thickness of the preliminary separator was 14 μm, the ventilation time was 132 sec/100 cc, the total thickness of the final separator including the adhesive layer was 15 μm, and the ventilation time was 179 sec/100 cc.

At this time, the difference in solubility parameter between the first binder polymer and the second binder polymer was 0.1 MPa ^1/2 .

Example 3

30 parts by weight of PEI resin (Sabic Ultem 1000, glass transition temperature 217° C.) is used as a heat-resistant polymer, and 10 parts by weight of PVdF-HFP resin (Arkema LBG, melting point 152° C., weight average molecular weight 740,000) as the first binder polymer A separator was prepared in the same manner as in Example 1, except that it was used. The total thickness of the preliminary separator was 14 μm, the ventilation time was 153 sec/100 cc, the total thickness of the final separator including the adhesive layer was 15 μm, and the ventilation time was 201 sec/100 cc.

The solubility parameter of the first binder polymer and the second binder polymer was measured using the above-described method. δD, δP, and δH values of the first binder polymer were 17.2, 12.5, and 8.2, respectively. δD, δP, and δH values of the second binder polymer were 17.2, 12.5, and 8.2, respectively.

At this time, the difference in solubility parameter between the first binder polymer and the second binder polymer was 0.0 MPa ^1/2 .

Example 4

Preparation of the preliminary separator was carried out in the same manner as in Example 1. Then, when forming the adhesive layer, 2 parts by weight of PVdF-HFP resin (Solvay's Solef21510, melting point 135° C., weight average molecular weight 280,000) as a second binder polymer was added to NMP to prepare a composition for forming an adhesive layer. The composition for forming an adhesive layer was coated on both sides of the separator by a dip coating method using the composition for forming an adhesive layer thus prepared, followed by immersion in a coagulation bath composed of 80:20 water and NMP to phase-separate. The total thickness of the final separator was 15 μm, and the aeration time was 175 sec/100 cc.

The solubility parameter of the first binder polymer and the second binder polymer was measured using the above-described method. δD, δP, and δH values of the first binder polymer were 17.2, 12.5, and 8.2, respectively. δD, δP, and δH values of the second binder polymer were 17.2, 12.5, and 8.2, respectively. At this time, the difference in solubility parameter between the first binder polymer and the second binder polymer was 0.0 MPa ^1/2 .

Example 5

A separator was prepared in the same manner as in Example 4, except that 20 parts by weight of alumina (Alu65 by Evonik) was added to the composition of the adhesive layer compared to the second binder polymer. The total thickness of the final separator was 15 μm, and the ventilation time was 162 sec/100 cc.

Example 6

26 parts by weight of PEI resin (Sabic Ultem 1000, glass transition temperature 217° C.) is used as a heat-resistant polymer, and 4 parts by weight of PVdF-HFP resin (Arkema LBG, melting point 152° C., weight average molecular weight 740,000) as the first binder polymer A separator was prepared in the same manner as in Example 1, except that it was used.

The total thickness of the preliminary separator was 14 μm, the ventilation time was 162 sec/100 cc, the total thickness of the final separator including the adhesive layer was 15 μm, and the ventilation time was 209 sec/100 cc.

The solubility parameter of the first binder polymer and the second binder polymer was measured using the above-described method. δD, δP, and δH values of the first binder polymer were 17.2, 12.5, and 8.2, respectively. δD, δP, and δH values of the second binder polymer were 17.2, 12.5, and 8.2, respectively. In this case, the solubility parameter difference between the first binder polymer and the second binder polymer was 0.0 MPa ^1/2 .

Comparative Example 1

A preliminary separator was prepared in the same manner as in Example 1 except that the first binder polymer was not applied. The prepared preliminary separator had a total thickness of 14 μm and a ventilation time of 161 sec/100 cc.

Subsequently, an adhesive layer was formed in the same manner as in Example 1, but the adhesive layer detached during the physical property measurement process, making it difficult to measure the physical properties.

Comparative Example 2

Example 1 except that 38 parts by weight of PEI resin (Sabic's Ultem 1000) was used as the heat-resistant polymer and 2 parts by weight of PVdF-HFP resin (Arkema's LBG, melting point 152° C., weight average molecular weight 740,000) was used as the first binder polymer A separator was prepared in the same manner as described above. The total thickness of the preliminary separator was 14 μm, the ventilation time was 159 sec/100 cc, the total thickness of the final separator including the adhesive layer was 15 μm, and the ventilation time was 211 sec/100 cc.

The solubility parameter of the first binder polymer and the second binder polymer was measured using the above-described method. δD, δP, and δH values of the first binder polymer were 17.2, 12.5, and 8.2, respectively. δD, δP, and δH values of the second binder polymer were 17.2, 12.5, and 8.2, respectively.

At this time, the difference in solubility parameter between the first binder polymer and the second binder polymer was 0.0 MPa ^1/2 .

Comparative Example 3

A separator was prepared in the same manner as in Example 1, except that 40 parts by weight of a PVdF-HFP resin (LBG from Arkema, melting point 152° C., weight average molecular weight 740,000) was used as the first binder polymer without using a heat-resistant polymer.

The total thickness of the preliminary separator was 14 μm, the aeration time was 130 sec/100 cc, the total thickness of the final separator including the adhesive layer was 15 μm, and the aeration time was 185 sec/100 cc.

The solubility parameter of the first binder polymer and the second binder polymer was measured using the above-described method. δD, δP, and δH values of the first binder polymer were 17.2, 12.5, and 8.2, respectively. δD, δP, and δH values of the second binder polymer were 17.2, 12.5, and 8.2, respectively. In this case, the solubility parameter difference between the first binder polymer and the second binder polymer was 0.0 MPa ^1/2 .

Evaluation Example 1: Heat shrinkage test

The prepared separator was cut into a square shape with a size of MD 10cm x TD 10cm, left in a constant temperature oven maintained at 180° C. for 30 minutes, and then the changed length was measured with a ruler to check the degree of heat shrinkage. Heat shrinkage was measured in the MD direction and the TD direction, respectively, and was calculated as a percentage (%) of the contracted length compared to the initial length. Table 1 below shows the thermal shrinkage rates for the separators of Examples 1 to 6 and Comparative Examples 1 to 3.

Evaluation Example 2: Adhesion test with electrode

After arranging two separators to face each other, the adhesive layer was passed through a roll heated to 100°C. At this time, the adhesive force between the adhesive layer and the electrode was predicted as the peeling force required to peel the two separators. The peeling force for the separators of Examples 1 to 6 and Comparative Examples 1 to 3 is shown in Table 1 below.

Evaluation Example 3: Peel strength test result between the heat-resistant layer and the adhesive layer

After attaching the tape to the adhesive layer, the peeling force between the heat-resistant layer and the adhesive layer was measured in the form of peeling the tape. The peeling positions and peeling force between the heat-resistant layer and the adhesive layer for the separators of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1 below.

As can be seen in Table 1, in Examples 1 to 6 in which the first binder polymer was included in an amount of 10 parts by weight or more based on 100 parts by weight of the heat-resistant polymer, it was confirmed that both the heat shrinkage rate and the electrode adhesion were excellent. In addition, it was confirmed that the peeling force between the heat-resistant layer and the adhesive layer was large and the peeling did not easily occur between the heat-resistant layer and the adhesive layer.

On the other hand, in Comparative Example 1 in which the first binder polymer was not used, peeling occurred between the heat-resistant layer and the adhesive layer, and it was confirmed that the adhesive force of the adhesive layer was impossible to be realized. In addition, in Comparative Example 2, in which the first binder polymer was included in an amount of less than 10 parts by weight based on 100 parts by weight of the heat-resistant polymer, the first binder polymer was not sufficiently included in the heat-resistant layer, so it was confirmed that peeling still occurred between the heat-resistant layer and the adhesive layer. . In Comparative Example 3 in which no heat-resistant polymer was used, it was confirmed that the heat shrinkage rate was excessive.

1, 2: Separator
100, 200: porous substrate
110, 210: heat-resistant layer
120, 220: adhesive layer

Claims (14)

porous substrate;
a heat-resistant layer positioned on at least one surface of the porous substrate and including a heat-resistant polymer and a first binder polymer; and
It is located on the surface of the heat-resistant layer, the adhesive layer comprising a second binder polymer; includes,
The heat resistant polymer is a crystalline heat resistant polymer having a melting point (melting temperature, T _m ) of 250 ° C. or higher, or an amorphous heat resistant polymer having a glass transition temperature (Tg) of 200 ° C. or higher, or a combination thereof,
The difference between the solubility parameter of the first binder polymer and the second binder polymer is 5.0 MPa ^1/2 or less,
The separator for an electrochemical device, characterized in that the first binder polymer is included in the heat-resistant layer in an amount of 10 to 100 parts by weight based on 100 parts by weight of the heat-resistant polymer. According to claim 1,
The second binder polymer is a separator for an electrochemical device, characterized in that it has a melting point of 150 ℃ or less. According to claim 1,
The heat-resistant polymer is polyacetal, polysulfone (PSF), polyethersulfone (PES), polyetherimide (PEI), polyphenylenesulfide (PPS), polyetheretherketone (PEEK), polyarylate (PA) , polycarbonate, polyamideimide (PAI), polyimide (PI), polyamide, wholly aromatic polyamide (aramid), polyphenylene oxide, polybutylene terephthalate, polyethylene terephthalate, polyether ketone, or any of these A separator for an electrochemical device, comprising two or more. 3. The method of claim 2,
The second binder polymer is polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-tetrafluoroethylene, polyvinylidene fluoride- A separator for an electrochemical device comprising co-trifluoroethylene, polyvinylidene fluoride-co-trifluorochloroethylene, polyvinylidene fluoride-co-ethylene, or two or more of these. According to claim 1,
The heat-resistant layer is a separator for an electrochemical device, characterized in that it further comprises inorganic particles. According to claim 1,
The adhesive layer is a separator for an electrochemical device, characterized in that it further comprises inorganic particles. Preparing a porous substrate (S1);
Preparing a composition for forming a heat-resistant layer comprising a heat-resistant polymer, a first binder polymer, and a first solvent (S2);
forming a heat-resistant layer by coating the composition for forming a heat-resistant layer on at least one surface of the porous substrate (S3); and
and coating a composition for forming an adhesive layer comprising a second binder polymer and a second solvent on the surface of the heat-resistant layer to form an adhesive layer (S4);
_{The heat resistant polymer is a crystalline heat resistant polymer having a melting point (melting temperature, T m} ) of 250 ° C. or higher, an amorphous heat resistant polymer having a glass transition temperature (Tg) of 200 ° C. or higher, or a combination thereof,
The difference between the solubility parameter of the first binder polymer and the second binder polymer is 5.0 MPa ^1/2 or less,
The method of manufacturing a separator for an electrochemical device, characterized in that the first binder polymer is included in the composition for forming the heat-resistant layer in an amount of 10 to 100 parts by weight based on 100 parts by weight of the heat-resistant polymer. 8. The method of claim 7,
The method of manufacturing a separator for an electrochemical device, characterized in that the first binder polymer has a solubility of 5 wt % or more at 25° C. with respect to the first solvent. 8. The method of claim 7,
After the step (S3) of forming the heat-resistant layer is coated with a composition for forming a heat-resistant layer comprising the heat-resistant polymer, the first binder polymer, and the first solvent on at least one surface of the porous substrate, a first non-solvent is included A method of manufacturing a separator for an electrochemical device, comprising the step of phase separation by immersion in a coagulating solution. 8. The method of claim 7,
In the step (S4) of forming the adhesive layer, the composition for forming an adhesive layer including the second binder polymer and a second solvent is coated on the surface of the heat-resistant layer, and then phase separated by immersion in a coagulating solution containing a second non-solvent. A method of manufacturing a separator for an electrochemical device, comprising the step of: 8. The method of claim 7,
The step of forming the adhesive layer (S4) includes coating the composition for forming an adhesive layer including the second binder polymer and the second solvent on the surface of the heat-resistant layer, and then performing phase separation under a second non-solvent atmosphere in the gas phase. A method of manufacturing a separator for an electrochemical device, characterized in that 12. The method of claim 10 or 11,
For an electrochemical device, characterized in that the first binder polymer has a solubility of 10% by weight or less at 25°C in the second solvent and 2% by weight or less at 25°C in the second non-solvent A method for manufacturing a separator. 12. The method of claim 11,
When the second non-solvent is water,
After the step of forming the adhesive layer (S4) is coated with the composition for forming an adhesive layer comprising the second binder polymer and the second solvent on the surface of the heat-resistant layer, humidifying phase separation under a condition of 40 to 80% relative humidity. A method of manufacturing a separator for an electrochemical device, comprising: An electrochemical device comprising an anode, a cathode, and a separator interposed between the anode and the cathode, wherein the separator is the separator of any one of claims 1 to 6.

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