KR20140028510A - Separator for electrochemical cell with improved mechanical properties and method for preparing the same - Google Patents

Abstract

The present invention provides a separator for an electrochemical cell and a method for preparing the same. The separator has not only excellent mechanical strength and thermal resistance by uniaxial orientation at preset temperature after combining and pressing out a quasi-crystalline polymer composite and an amorphous polymer composite such as a high performance plastic but also an adequate ventilation path.

Description

Separator for electrochemical cell with improved mechanical properties and method for preparing the same}

The present invention relates to a separator for an electrochemical device with improved mechanical properties, and more particularly, to an amorphous polymer compound and semi-crystalline, which are a kind of high performance plastic. The present invention relates to a separator for an electrochemical device having a suitable balance between mechanical strength and air permeability by uniaxial stretching at a predetermined temperature after extruded by combining a polymer compound and a method of manufacturing the same.

As the demand for batteries as energy sources increases, the demand for and interest in lithium secondary batteries capable of charging and discharging are increasing.

The lithium secondary battery includes an electrode assembly composed of a positive electrode, a separator, and a negative electrode. The separator is a polymer membrane having a porous structure located between the positive electrode and the negative electrode, and provides a passage through which lithium ions can actively move, and also contacts the positive and negative electrodes. It plays a role to prevent. In addition, since the mechanical strength of the separator is also related to battery safety from external forces, many kinds of materials have recently been studied as separator materials, and one of them is an engineering plastic including a high performance plastic.

Engineering plastics, including high performance plastics, are sold in small quantities but much more expensive per unit weight than commodity plastics. Nevertheless, they are widely used in everyday articles because of their high heat resistance and mechanical strength. For example, polycarbonate is used for motorcycle helmets, and polyamide (nylon) is used for skiing and ski boots.

High performance plastics, also called super engineering plastics, are more expensive than conventional engineering plastics, but have much better heat resistance, mechanical strength, and chemical resistance.

These high performance plastics are further classified into amorphous engineering plastics and semi-crystalline engineering plastics.

The inventors have extruded a combination of a polymer compound belonging to an amorphous engineering plastic (hereinafter referred to as an amorphous polymer compound) and a polymer compound belonging to a semi-crystalline engineering plastic (hereinafter referred to as a 'quasi-crystalline polymer compound'). After uniaxial stretching at a predetermined temperature it was found that the membrane for an electrochemical device having excellent strength and air permeability can be obtained and led to the present invention.

The present invention is to provide a separator for an electrochemical device having excellent mechanical strength and heat resistance and a good balance of air permeability.

In addition, the present invention is to provide a method for manufacturing the separator for the electrochemical device.

In addition, the present invention is to provide an electrochemical device comprising the separator.

According to one aspect of the present invention, an amorphous polymer compound and a semi-crystalline polymer compound are included in a weight ratio of 1: 9 to 9: 1, and 10 sec / mL to 1000 sec / mL, more preferably, A separator for an electrochemical device having an air permeability of 100 sec / mL to 800 sec / mL is provided.

The electrochemical separator may have a network structure consisting of pores and nodes.

 The amorphous polymer compound may be a compound having a glass transition temperature of 120 ° C. or more.

The amorphous polymer compound may be one or a mixture of two or more selected from the group consisting of polyetherimide, polyethersulfone, cyclic olefin copolymer, polysulfone, polyarylsulfone, polycarbonate, modified polyphenylene oxide and thermoplastic urethane. have.

The amorphous high molecular compound may be polyetherimide, polyethersulfone or cyclic olefin copolymer.

The semi-crystalline high molecular compound may be a compound having a melting point of 200 ° C or higher.

The semi-crystalline polymer compound is polyetheretherketone, poly (p-phenylene sulfide), polytetrafluoroethylene, ethylene chlorotrifluoroethylene, fluorinated ethylene propylene copolymer, perfluoroalkoxy, nylon, polyethylene It may be one or a mixture of two or more selected from the group consisting of terephthalate and polybutylene terephthalate.

The semi-crystalline high molecular compound may be polyetheretherketone or poly (p-phenylene sulfide).

According to an aspect of the present invention, an electrochemical device comprising an anode, a cathode, a separator interposed between an anode and a cathode, and an electrolyte solution, wherein the separator is the above-described separator for electrochemical devices. Is provided.

The electrochemical device may be a lithium secondary battery.

According to an aspect of the present invention, in the method of manufacturing a separator for an electrochemical device, blending an amorphous polymer compound and a semi-crystalline polymer compound in a ratio of 1: 9 to 9: 1 by weight to obtain a blend composition ; Extruding the blend composition obtained in the form of a film at a temperature of 20 to 100 ° C. higher than the melting point of the semi-crystalline polymer compound; And uniaxially stretching the extruded product in the form of a film in a machine direction.

According to the present invention, not only having excellent mechanical strength and heat resistance, but also having an air permeability in the range of 10 sec / mL to 1000 sec / mL, a membrane for an electrochemical device having excellent air permeability can be obtained.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

In addition, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

According to the present invention, there is provided a separator for an electrochemical device prepared from a composition in which an amorphous polymer compound and a semi-crystalline polymer compound are blended in a 9: 1 to 1: 9 ratio by weight.

The amorphous polymer compound used in the present invention is a compound having a glass transition temperature of 120 ° C. or higher, and specific examples thereof include polyetherimide (PEI), polyethersulfone (PES), cyclic olefin copolymer (COC), polysulfone, and polyaryl. One or two or more kinds selected from the group consisting of sulfones, polycarbonates, modified polyphenylene oxides and thermoplastic urethanes, but are not limited thereto. The amorphous polymer compound may be prepared and used by a conventional method in the art, but may be obtained by using a commercially available product.

More preferred amorphous polymer compounds of the present invention are polyetherimide (PEI), polyethersulfone (PES), and cyclic olefin copolymer (COC).

The polyetherimide compounds usable in the present invention are, for example, polyetherimide having the following repeating units, or melting, for example, glass transition temperature (T _g ) of about 220 ° C., 17.8 g / 10 min (337 ° C./6.6 Kg) It has a flow index (MI) and a heat deflection temperature (HDT) of 200 ° C., but is not limited thereto.

Wherein n is an integer of 1 or more.

The polyethersulfone compounds usable in the present invention are, for example, compounds having a glass transition temperature (T _g ) of about 220 ° C., but are not limited thereto.

The cyclic olefin copolymer usable in the present invention is, for example, a compound having a glass transition temperature (T _g ) of about 150 ° C., but is not limited thereto.

The semi-crystalline high molecular compound used in the present invention is a compound having a melting point of 200 ° C. or higher, and specific examples thereof include polyaryl ether ketone (PAEK), particularly, polyether ether ketone (PEEK); Poly (p-phenylene sulfide) (PPS); Polytetrafluoroethylene (PTFE); Ethylene chlorotrifluoroethylene (ECTFE); Fluorinated ethylene propylene copolymers (FEP); Perfluoroalkoxy (PFA); nylon; Polyethylene terephthalate (PET); Polybutylene terephthalate (PBT) and the like, but is not limited thereto. The quasi-crystalline polymer compound may also be prepared and used by conventional methods in the art, but may be obtained by using a commercially available product.

More preferred semi-crystalline polymer compounds of the present invention are polyetheretherketone (PEEK), poly (p-phenylene sulfide) (PPS).

The polyether ether ketone compound usable in the present invention is, for example, a compound having the following repeating unit, or, for example, a glass transition temperature (T _g ) of 150 ° C., melting point (T _m ) of 340 ° C., 10 g / 10 minutes (400). 17 ° C./2.16 Kg) melt flow index (MI), compound having a heat deflection temperature (HDT) of 160 ° C., or a glass transition temperature (T _g ) of 155 ° C., melting point (T _m ) of 370 ° C., 17 g It has a melt flow index (MI) of 10 minutes (410 ° C./5) and a heat deflection temperature (HDT) of 167 ° C., but is not limited to:

Where

Ar is independently a divalent aromatic radical selected from phenylene, biphenylene or naphthylene,

X is independently O, C (= O) or a direct bond,

n is a number from 0 to 3,

b, c, d and e are 0 or 1,

a is an integer of 1-4.

More specifically, the polyetheretherketone may have, for example, the following repeating units, but is not limited to:

The poly (p-phenylene sulfide) usable in the present invention includes, for example, a compound including the following repeating unit and a derivative thereof, or, for example, a glass transition temperature (T _g ) of 92 ° C. and a melting point (T _m ) of 280 ° C. Have, but are not limited to:

According to the present invention, amorphous polymer compounds and quasi-crystalline polymer compounds are used in a ratio of 9: 1 to 1: 9 by weight. When the amorphous polymer compound is added to the quasi-crystalline polymer compound, the glass transition temperature of the composition is higher than when the quasi-crystalline polymer compound is present alone. Therefore, when the addition ratio of the amorphous polymer compound is less than the above-mentioned ratio, the glass transition temperature increase effect is small and heat resistance may be insufficient. In addition, the presence of the semi-crystalline high molecular compound alone may not only accelerate thermal nucleation but also greatly increase crystals, which may adversely affect the transparency and deformation of the crystals. Therefore, crystallization is delayed by adding an amorphous polymer compound. If the addition ratio of the amorphous polymer compound is more than the aforementioned ratio, the crystallization rate becomes too slow. Therefore, within the range described above, as the content of the semi-crystalline polymer compound decreases and the content of the amorphous polymer compound increases, the air permeability tends to increase, thereby providing a desirable air permeability as a separator for an electrochemical device.

In addition to the amorphous polymer compound and the semi-crystalline polymer compound, the blend composition of the present invention may include various additives such as inorganic particles and binders within a range that does not adversely affect the properties of the composition.

In the present invention, the inorganic particles may be added to further improve the dimensional stability of the separator. The inorganic particles may be selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transfer ability, and mixtures thereof. The inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr _x , Ti _{1 -x} ) O ₃ (PZT, 0 <x <1), Pb _{1- x} La _x Zr _1-y Ti _y O ₃ (PLZT, 0 <x <1, 0 < y <1), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 - x PbTiO 3 (PMN-PT, 0 <x <1), hafnia ( _{HfO 2), SrTiO 3, SnO} 2, CeO 2, MgO, NiO, CaO, ZnO, ZrO 2, SiO 2, Y 2 O 3, Al 2 O 3, SiC and one or two selected from the group consisting of TiO ₂ It may be a mixture of species or more. In addition, the inorganic particles having a lithium ion transfer ability are lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), lithium aluminum Titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), lithium nitride (Li _x N _y , 0 <x <4, 0 <y <2), SiS ₂ (Li _x Si _y S _z , 0 <x <3, 0 <y <2, 0 <z <4) Series glass and P ₂ S ₅ (Li _x P _y S _z , 0 <x <3, 0 <y <3, 0 <z <7) It may be one or a mixture of two or more selected from the group consisting of glass. The inorganic particles may be included in an amount of 10 to 200 parts by weight based on 100 parts by weight of the total weight of the amorphous polymer compound and the semi-crystalline polymer compound. If less than the lower limit, there is no effect on the dimensional stability, if more than the upper limit may reduce the mechanical strength of the separator.

Separation membrane for an electrochemical device of the present invention comprises the steps of blending the amorphous polymer compound and the semi-crystalline polymer compound in a weight ratio of 9: 1 to 1: 9 to obtain a blend composition; Extruding the blend composition obtained in the form of a film at a temperature of 20 to 100 ° C. higher than the melting point of the semi-crystalline polymer compound; And uniaxially stretching the extruded product in the form of a film in a mechanical direction (MD).

The first step of the preparation method according to the present invention is a blending of the amorphous polymer compound and the semi-crystalline polymer compound in a 9: 1 to 1: 9 ratio by weight. As the blending method, conventional methods known in the art may be used. For example, the semi-crystalline polymer compound and the amorphous polymer compound may be mechanically mixed and blended together with an additive by a kneader or the like as necessary.

The second step of the production process according to the invention is the step of extruding the blend composition obtained in the form of a film at a temperature of 20 to 100 ° C. higher than the melting point of the semi-crystalline polymer compound. In the extrusion according to the present invention, a known method such as an extrusion casting method using a T-die or a leading edge method may be used, but is not limited thereto. The film thickness can be adjusted to about 50-500 μm by extrusion.

The third step of the manufacturing method according to the present invention is the step of uniaxially stretching the resulting product in the form of a film in the machine direction. The extrusion result in the form of a film is uniaxially stretched at a predetermined rate, for example, 10% / s to 25% / s. Uniaxial stretching causes strain-induced crystallization in the semi-crystalline high molecular compound, and the highly oriented crystals generated form nodes of the network. As used herein, the term 'node' refers to a portion in which polymer chains are formed to cross each other, and may correspond to vertices of pores formed by cross chains. As used herein, the term “pore” refers to a part that exists in the separator for an electrochemical device, and allows a smooth movement of lithium ions through the pores and fills a large amount of electrolyte to show a high impregnation rate. Once such highly oriented nodes are formed, the degree of alignment of the crystalline domains increases very rapidly with the draw ratio. Amorphous polymer compounds delay the rate of crystallization of orientation of semi-crystalline polymer compounds, thereby increasing the overall chain orientation. Once the stretching is completed, the stretched film may be cooled with cold air or the like to prevent further relaxation.

The manufacturing method of the present invention may add other processes or modify some processes within the scope of not damaging the effects of the invention, and these should be construed as being included in the scope of the present invention. The separator for an electrochemical device according to the present invention prepared as described above may have pores having a long diameter (longest diameter) in the range of 0.1 to 70 μm. In addition, the separator for an electrochemical device according to the present invention may have an air permeability in the range of 10 sec / 100 mL to 1,000 sec / 100 mL or a air permeability in the range of 100 sec / 100 mL to 800 sec / 100 mL. In addition, the separator for an electrochemical device according to the present invention may have a porosity in the range of 30 to 60%. The thickness of the separator for an electrochemical device according to the present invention is not particularly limited, but is preferably 1 to 100 μm or 5 to 50 μm.

According to the present invention, an electrode assembly used in an electrochemical device can be manufactured by laminating the thus-produced film between a cathode and an anode to use as a separator. The electrochemical device includes all devices that perform an electrochemical reaction, and specific examples include capacitors such as all kinds of primary, secondary, fuel cell, solar cell, or super-capacitor devices. Particularly, 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 is preferable.

The positive electrode and the negative electrode to be used together with the separator of the present invention are not particularly limited, and the electrode active material may be bound to an electrode current collector according to a conventional method known in the art. Examples of the cathode active material include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof It is preferable to use a 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 a negative electrode of an electrochemical device can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium-adsorbing materials such as graphite or other carbon-based materials and the like are preferable. Non-limiting examples of the positive electrode current collector is a foil produced by aluminum, nickel or a combination thereof, and non-limiting examples of the negative electrode current collector by copper, gold, nickel or copper alloy or a combination thereof Foils produced.

The electrolytic solution that can be used in the electrochemical device of the present invention is a salt of a structure such as A ⁺ B ^- 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), ethylmethylcarbonate (EMC), gamma butyrolactone (g- Butyrolactone) or a mixture thereof, or dissolved in an organic solvent, but not limited thereto, wherein A ⁺ is an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ , or a combination thereof including consisting of ions, wherein 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} ^- is included with the ions made of such anions, or a combination thereof ^{_{-, C (CF 2 SO 2}} ) 3. The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and the required physical properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

As a process for applying the separation membrane according to an embodiment of the present invention, a lamination, stacking and folding process of a separation membrane and an electrode can be performed in addition to a general winding process.

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Example  1-5: Preparation of separator

The semi-crystalline polymer compound and the amorphous polymer compound disclosed in Table 1 below were mechanically mixed in the proportions (wt%) disclosed in Table 1, and dried in a vacuum oven at 140 ° C. for 24 hours. The resulting dry material was then melt mixed at a extrusion temperature of 410 ° C. using a twin screw extruder and then extruded into a film of 150 μm thickness. Subsequently, the extruded film was uniaxially stretched in the machine direction at a rate of 20% / s at a stretching temperature of 250 ° C. using a drawing machine to obtain a separator for an electrochemical device.

Comparative Example  1-5: Preparation of separator

Separation membrane for an electrochemical device was prepared in the same manner as in Examples 1 to 5 by applying the kind and ratio (wt%), extrusion temperature and stretching temperature of the semicrystalline polymer compound and amorphous polymer compound described in Comparative Examples 1 to 5 of Table 1 Obtained.

Experimental Example Thickness and air permeability

The separator obtained in each of Examples 1 to 5 and Comparative Examples 1 to 5 was cut to 5 cm x 5 cm, and then the thickness thereof was measured. The time taken by 100 mL of air was measured using a Gurley Type Densometer manufactured by Toyoseki. The results are shown in Table 1 below.

Semicrystalline Polymer Amorphous polymer Extrusion temperature
(℃) Stretching temperature
(℃) thickness
(um) Ventilation
(sec / 100 mL) Kinds weight% Kinds weight% Example 1 PEEK ¹ 90 PEI 10 410 250 25 to 30 650 Example 2 PEEK ¹ 75 PEI 25 410 250 25 to 30 600 Example 3 PEEK ¹ 50 PEI 50 410 250 25 to 30 550 Example 4 PEEK ¹ 25 PEI 75 410 250 25 to 30 500 Example 5 PEEK ¹ 10 PEI 90 410 250 25 to 30 400 Comparative Example 1 PEEK ¹ 100 PEI 0 410 250 25 to 30 ∞ Comparative Example 2 PEEK ¹ 0 PEI 100 410 250 25 to 30 2000 Comparative Example 3 PEEK ¹ 75 PEI 25 410 230 25 to 30 5000 Comparative Example 4 PEEK ² 75 COC 25 400 160 25 to 30 8000 Comparative Example 5 PPS 75 PES 25 350 230 25 to 30 6500 PEEK ¹ : Polyaryl Ether Ketone, Korea Engineering Plastics Co., Ltd., 9300CR
PEEK ² : Polyetheretherketone, Solvay, KetaSpire (registered trademark) KT-851
PPS: poly (p-phenylene sulfide), Toray, glass transition temperature 92 ℃, melting point 280 ℃
PEI: polyetherimide, SABIC company, Ultem (registered trademark) 1010R
PES: Polyethersulfone, BASF, Ultrason E2020P
COC: cyclic olefin copolymer, Topas Advanced Polymers, Topas® 6015S-04

The lithium secondary battery  Produce

(1) Preparation of positive electrode

90 parts by weight of lithium manganese oxide as a positive electrode active material, 5 parts by weight of carbon black as a conductive material, and 5 parts by weight of polyvinylidene fluoride (PVdF) as a binder, N-methyl-2-pyrrolidone (NMP) as a solvent. 40 parts by weight of the positive electrode active material slurry was prepared. The positive electrode active material slurry was applied to an aluminum (Al) thin film of a positive electrode current collector having a thickness of 100 μm and dried to prepare a positive electrode, and then roll press was performed.

(2) Manufacture of cathodes

Add 95 parts by weight, 2 parts by weight, and 3 parts by weight of carbon powder as a negative electrode active material, PVdF as a binder, and 3 parts by weight of conductive material, respectively, and add 100 parts by weight of N-methyl-2-pyrrolidone (NMP) as a solvent. The negative electrode active material slurry was prepared. The negative electrode active material slurry was applied to a copper (Cu) thin film, which is a negative electrode current collector having a thickness of 90 μm, to prepare a negative electrode through drying, and then roll press was performed.

(3) Manufacture of lithium secondary battery

The unit cells were assembled by stacking the positive electrode and the negative electrode prepared in the above-described method, and the separators prepared in Examples 1 to 5, respectively. Then, an electrolyte solution (ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) = 3/2/5 (volume ratio), 1 mol of lithium hexafluorophosphate (LiPF ₆ )) was injected into the A secondary battery was manufactured.

Claims (12)

Amorphous polymer compound and semi-crystalline polymer compound are included in a weight ratio of 9: 1 to 1: 9,
Separation membrane for an electrochemical device having an air permeability ranging from 10 sec / 100 mL to 1000 sec / 100 mL.
The method of claim 1,
Separation membrane for an electrochemical device, characterized in that the air permeability ranges from 100 sec / 100 mL to 800 sec / 100 mL.
The method of claim 1,
Separation membrane for an electrochemical device, characterized in that it has a network structure consisting of pores and nodes.
The method of claim 1,
Separation membrane for an electrochemical device, characterized in that the amorphous polymer compound is a compound having a glass transition temperature of 120 ℃ or more.
The method of claim 1,
The amorphous polymer compound is one or a mixture of two or more selected from the group consisting of polyetherimide, polyethersulfone, cyclic olefin copolymer, polyarylsulfone, polycarbonate, modified polyphenylene oxide and thermoplastic urethane Separators for Electrochemical Devices.
6. The method of claim 5,
Separation membrane for an electrochemical device, characterized in that the amorphous polymer compound is polyetherimide, polyethersulfone or cyclic olefin copolymer.
The method of claim 1,
Separation membrane for an electrochemical device, characterized in that the quasi-crystalline polymer compound is a compound having a melting point of 200 ℃ or more.
The method of claim 1,
The semi-crystalline polymer compound is polyetheretherketone, poly (p-phenylene sulfide), polytetrafluoroethylene, ethylene chlorotrifluoroethylene, fluorinated ethylene propylene copolymer, perfluoroalkoxy, nylon, polyethylene Separation membrane for an electrochemical device, characterized in that one or two or more selected from the group consisting of terephthalate and polybutylene terephthalate. 9. The method of claim 8,
Separation membrane for an electrochemical device, characterized in that the quasi-crystalline polymer compound is polyetheretherketone or poly (p-phenylene sulfide).
1. An electrochemical device comprising an anode, a cathode, a separator interposed between the anode and the cathode, and an electrolyte,
The electrochemical device according to any one of claims 1 to 9, wherein the separation membrane is a separation membrane for an electrochemical device.
11. The method of claim 10,
Wherein the electrochemical device is a lithium secondary battery.
A method for producing a separator for an electrochemical device,
Blending the amorphous polymer compound with the semi-crystalline polymer compound in a weight ratio of 9: 1 to 1: 9 to obtain a blend composition;
Extruding the blend composition obtained at a temperature of 20 to 100 ° C. higher than the melting point of the semi-crystalline polymer compound to form a film; And
Uniaxially stretching the film-shaped extrusion result in the machine direction
Wherein the separator is formed of a metal.