KR20150050498A - Porous composite separator incorporated with inorganic particles, electrochemical device comprising the same, and method of preparing the separator - Google Patents

Abstract

The present invention provides a porous separating film including a porous film which is made of a porous polyolefin gel film, wherein 50-90 parts by weight of first inorganic particles and 10-20 parts by weight of second inorganic particles are dispersed based on 100 parts by weight of inorganic particles. The separating film according to the present invention achieves the mechanical strength and the high porosity of the separating film for thickness direction while having a thin thickness, and the structural and thermal stability of the separating film by the inorganic particles which are regularly dispersed inside the gel film.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a porous separator in which inorganic particles are mixed, an electrochemical device including the porous separator, and a method of manufacturing the separator. [0002]

The present invention relates to a porous separator, and more particularly, to a porous separator containing inorganic particles, an electrochemical device including the same, and a process for producing the separator.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. The electrochemical device is one of the most attracting fields in this respect, and development of a secondary battery such as a rechargeable lithium secondary battery has become a focus of attention.

In the separator constituting such a battery, the basic required characteristics thereof are excellent air permeability, low heat shrinkage and high puncture strength, similar to that of the separator for other cells, and are continuously excellent due to the development of high capacity and high output cells The air permeability is further required. However, the porous separator of the secondary battery exhibits extreme heat shrinkage behavior at a temperature of about 100 캜 or more due to the characteristics of the manufacturing process including material properties and elongation, thereby causing a short circuit between the anode and the cathode. In order to solve such a problem of safety of the battery, for example, Korean Patent Publication No. 2007-0083975 (Hitachi) and Korean Patent Laid-Open Publication No. 2007-0019958 (Ebonic) disclose a method for producing a battery comprising a mixture of insulating filler particles and a binder Discloses a separation membrane prepared by adding a substance having a shut-down function to a porous coating layer while providing a porous coating layer formed thereon.

On the other hand, the wet production method is a single layer film type in which pores are formed on both sides of a film by extrusion and chemical treatment using a polyolefin-based polymer resin as a base raw material, and the process is relatively complicated. Typically, the film is deformed by heat shrinkage under high temperature conditions, And there is a possibility that stability can not be secured.

Therefore, there is still a need for a separator that largely solves the porosity reduction due to shrinkage in the thickness direction while maintaining thermal and mechanical properties.

Therefore, a problem to be solved by the present invention is to provide a thin membrane having excellent thermal and mechanical properties, and a large porosity. It is also to be easily understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

The present invention provides a porous separator for solving the above-mentioned technical problems. The separation membrane includes a porous film, wherein the porous film contains a polyolefin-based polymer and a plurality of inorganic particles, and a plurality of pores are formed.

Wherein the inorganic particles comprise 50 to 90 parts by weight of the first inorganic particles and 10 to 50 parts by weight of the second inorganic particles with respect to 100 parts by weight of the total of the inorganic particles, May be smaller than the average particle diameter of the inorganic particles.

Here, the polyolefin-based polymer resin may be one or two or more polymers or copolymers selected from the group consisting of ethylene, propylene, 1-butene, 4-methyl-1-pentene, Or a mixture of two or more of them.

Here, the porous film may include 10 to 30 parts by weight of inorganic particles relative to 100 parts by weight of the film.

Here, the inorganic particles may include inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transporting ability, or a mixture thereof.

The inorganic particles having a dielectric constant of 5 or more are preferably 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 1, 0 < y < 1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPbTiO ₃ (PMN- (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 TiO ₂ Or a mixture of two or more.

Here, the surface of the inorganic particle can be modified with an organic polymer. Here, the thickness of the porous separation membrane may be between 5 탆 and 20 탆.

Here, the first inorganic particles may have an average particle diameter of 5 nm to 100 nm, and the second inorganic particles may have an average particle diameter of 100 nm or more and 1,000 nm or less.

The present invention also provides an electrochemical device comprising an anode, a cathode, and a separator interposed between the anode and the cathode, wherein the separator is any one of the porous separators according to the present invention.

The present invention also relates to a method for preparing a mixture comprising: (S1) preparing a mixture comprising a polymer resin, inorganic particles and a pore-forming agent; (S2) a step (S2) of obtaining an unstretched film by extruding the mixture of (S1); (S3) annealing the unstretched film of (S2); (S4) stretching the unstretched film of (S3); And (S5) removing the pore-forming agent to form a porous film.

Here, the extrusion of (S1) may be performed at a temperature of 150 to 300 캜.

Here, the inorganic particles include first inorganic particles and second inorganic particles, and the average particle diameter of the first inorganic particles may be smaller than the average particle diameter of the second inorganic particles.

The separation membrane according to the present invention can achieve the mechanical strength and high porosity of the separation membrane with respect to the thickness direction while being thin, and the structural and thermal stability of the separation membrane by the inorganic particles uniformly dispersed in the film.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given above, serve to better understand the spirit of the invention. And should not be construed as limiting.
1 is an example of a cross-sectional view of a porous separation membrane produced according to one embodiment of the present invention.
Fig. 2 shows a change in the load distribution in the thickness direction of the prior art separator.
FIG. 3 is a graph showing a change in load in a thickness direction of a porous separation membrane manufactured according to an embodiment of the present invention.
4 is a schematic flow diagram of a method for producing a porous separation membrane according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. Prior to this, 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 designate the concept of a term appropriately in order to describe its own invention in the best way possible. It should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in this 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, It is to be understood that equivalents and modifications are possible.

According to one aspect of the present invention, there is provided a porous separator comprising a porous film comprising a polyolefin-based polymer resin and a plurality of inorganic particles. The polymer film is characterized in that inorganic particles are incorporated therein.

1 is an example of a cross-sectional view of a porous separation membrane produced according to one embodiment of the present invention. FIG. 1 is a schematic drawing of a porous film according to the present invention. First inorganic particles having a small particle diameter and second inorganic particles having a large particle diameter are mixed and dispersed in a fibril of a porous film. 1 is a specific embodiment of the porous separator of the present invention, and is not limited thereto.

The porous separator according to an embodiment of the present invention includes a porous film formed by extruding and stretching a polyolefin-based polymer resin, and the film is formed by mixing two types of inorganic particles having different average particle diameters.

The film has a porous structure having a plurality of pores, and includes a polyolefin-based polymer resin. Non-limiting examples of the polyolefin-based polymer resin include one or two or more polymers or copolymers selected from the group consisting of ethylene, propylene, 1-butene, 4-methyl-1-pentene, But are not limited to, a combination of two or more thereof. In order to easily realize the porosity at the surface of the polyolefin film, various phase separation methods can be used.

In one specific embodiment of the present invention, the inorganic particles include a first inorganic particle and a second inorganic particle. The first inorganic particles and the second inorganic particles each independently have an oxidation and / or reduction reaction in an operating voltage range of the applied electrochemical device (for example, about 0 to about 5 V based on Li / Li ⁺ ) And is not particularly limited. Particularly, when inorganic particles having a high dielectric constant are used as the inorganic particles, the dissociation of the electrolyte salt, for example, the lithium salt in the liquid electrolyte, can be increased, and the ion conductivity of the electrolyte can be improved.

Although the kind of the inorganic particles is not particularly limited, inorganic particles selected from the group consisting of inorganic particles having a dielectric constant of about 5 or more, inorganic particles having a lithium ion transferring ability (in the case of a lithium secondary battery), and mixtures thereof may be used . The inorganic particles having a dielectric constant of about 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 (PMN-PT, 0 < x < 1), and half (PZT, 0 <x <1, 0 <y <1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPbTiO ₃ It is preferable to use 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 TiO ₂ , But is not limited thereto. As the inorganic particles having lithium ion transferring ability, lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (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 <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 , x <4, 0 <y < 1, 0 <z <1, 0 <w <5), lithium nitrides _{(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) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 < z < 7) series glass or the like is preferably used, but is not limited thereto.

The first inorganic particle is a relatively small-sized inorganic particle as compared with the second inorganic particle described later. The first inorganic particles preferably have an average particle diameter of about 5 nm to about 100 nm, more preferably inorganic particles having an average particle diameter of about 10 nm to about 50 nm. The first inorganic particles having an average particle diameter in this range are very tightly bonded and arranged in the porous polyolefin film due to their small particle size. The first inorganic particles in the porous polyolefin film having such a tight arrangement function to prevent heat shrinkage of the separator due to changes in the interior or exterior.

On the other hand, the second inorganic particles are relatively large-sized inorganic particles as compared with the first inorganic particles. This second inorganic particle has an average particle size of from about 100 nm to about 1,000 nm, preferably from about 200 nm to about 800 nm. The second inorganic particle having an average particle diameter in this range has a large particle size, so that the space between bound particles in the porous polyolefin film is very wide. Further, for the above-mentioned reason, the film contains 50 to 90 parts by weight of the first inorganic particles, preferably about 50 to about 70 parts by weight, based on 100 parts by weight of the total of the inorganic particles (the first inorganic particles and the second inorganic particles) And 10 to 50 parts by weight, preferably about 30 to 50 parts by weight, of the second inorganic particles are dispersed.

Fig. 2 shows a change in the load distribution in the thickness direction of the prior art separator. Referring to FIG. 2, since only the polymer exists in the separation membrane according to the prior art without inorganic particles, the distance (space) inside the separation membrane is easily reduced by the load, and consequently, The porosity of the membrane also decreases.

FIG. 3 is a graph showing a change in load in a thickness direction of a porous separation membrane manufactured according to an embodiment of the present invention. 3, in the separator according to the embodiment of the present invention, unlike the separator of the prior art of FIG. 2, the first inorganic particles and the second inorganic particles having different average particle diameters are uniformly dispersed in the porous polyolefin film So that the unique characteristics of each of the inorganic particles can be exhibited in combination. That is, the thermal and mechanical strengths are improved due to the incorporated inorganic particles. Particularly, the first inorganic particles having a relatively small average particle diameter inhibit heat shrinkage of the separator to improve the thermal strength and have a relatively large average particle diameter The second inorganic particles can prevent the reduction of the thickness and the porosity of the separation membrane, thereby improving the mechanical strength.

The porous polyolefin film may comprise about 10 to about 30 parts by weight of the inorganic particles (i.e., the total amount of the first inorganic particles and the second inorganic particles) based on 100 parts by weight of the film. When the inorganic particles are contained in the porous polyolefin film in the above-described range, the inorganic particles can form a separation membrane having excellent ionic conductivity and electrolyte impregnation as well as structural and thermal stability.

In addition, the first inorganic particles and the second inorganic particles may each independently have their surface modified with an organic material, and the organic material may include, without limitation, carboxylic acid, ketone and CONH having 6 to 18 carbon atoms, It may be a mixture of two or more.

The thickness of the porous separation membrane may be from about 5 탆 to about 20 탆, preferably from about 7 탆 to about 20 탆

According to another aspect of the present invention, an electrochemical device including the positive electrode, the negative electrode, and the above-described separator interposed between the positive electrode and the negative electrode may be manufactured. The electrochemical device of the present invention includes all devices that perform an electrochemical reaction. Examples of the electrochemical device include capacitors such as all types of primary cells, secondary cells, fuel cells, solar cells, and super capacitors. 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 among the above secondary batteries.

The anode, the cathode and the like can be easily produced by a process and / or a method known in the art.

The anode is prepared by binding a cathode active material to a cathode current collector according to a conventional method known in the art. As the cathode active material, a conventional cathode active material that can be used for a cathode of a conventional electrochemical device can be used. Examples of the cathode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (0 <a <1, 0 <b <1, a + b + c = 1), LiNi _{1 -Y} Co _Y O ₂ , LiCo _{1 -Y} Mn _{Y 2} O, LiNi _{1 -Y} Mn _Y O ₂ (where, 0≤Y <1), Li ( Ni a Co b Mn c) O 4 (0 <a <2, 0 <b <2, a + b + c = 2), LiMn 2-Z Ni _Z O _4, LiMn include _2-Z Co _Z O ₄ (where, 0 <Z <2), LiCoPO 4, LiFePO 4 , and mixtures thereof. The anode current collector may be made of aluminum, nickel, or a combination thereof.

The negative electrode is prepared by adhering the negative electrode active material to the negative electrode current collector according to a conventional method known in the art. At this time, the negative electrode active material may be carbon such as non-graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1-x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides of Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 < x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, Bi ₂ O ₅ and the like; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used. On the other hand, as the negative electrode current collector, stainless steel, nickel, copper, titanium or an alloy thereof can be used.

Also, the electrolyte that can be inserted between the electrode and the separator is a salt having a structure such as A ⁺ B ^- , where A ⁺ includes an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ 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 - (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and the like, and salts containing anions such as C (CF ₂ SO ₂ ) ₃ ^- But are not limited to, dipropyl carbonate (DPC), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (? -butyrolactone), or a mixture thereof, but is not limited thereto All.

The electrolyte may be injected at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product.

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

According to another aspect of the present invention, a method of manufacturing a porous separator is provided. According to one embodiment of the present invention, the porous separation membrane can be manufactured by thermal induced phase separation, so the present invention is not limited thereto. According to an aspect of the present invention, there is provided a method for preparing a mixture comprising a polyolefin-based polymer resin, inorganic particles and a pore-forming agent (S1), extruding the mixture to obtain an unoriented film (S2), annealing the unstretched film (S3), stretching the unstretched film (S4), and removing the pore-forming agent to form a porous film (S5).

4 is a schematic flow diagram of a method for producing a porous separation membrane according to an embodiment of the present invention. A method of manufacturing the porous separation membrane of the present invention will be described with reference to FIG.

50 to 90 parts by weight of the first inorganic particles having an average particle diameter of 5 nm to 100 nm and 50 to 90 parts by weight of the second inorganic particles having an average particle diameter of more than 100 nm and 1,000 nm or less based on 100 parts by weight of the total of inorganic particles in the step (S1) And the polyolefin polymer and the pore-forming agent are mixed while stirring. In this mixture, the first inorganic particles and the second inorganic particles are uniformly dispersed. Here, the first inorganic particles, the second inorganic particles and the polyolefin polymer are as described in the description of the separator of the present invention.

Also, the mixture may contain about 10 to about 30 parts by weight of inorganic particles (i.e., the total amount of the first inorganic particles and the second inorganic particles) based on 100 parts by weight of the total of the polyolefin-based polymer particles and the inorganic particles. When the inorganic particles are contained in the above-mentioned range within the mixture, the inorganic particles can form a separation membrane having excellent ionic conductivity and electrolyte impregnability as well as structural and thermal stability.

The first inorganic particles and the second inorganic particles may each independently have their surface modified with an organic polymer. The organic polymer may include, but is not limited to, one selected from the group consisting of C6-C18-COOH, COR, Or a mixture of two or more.

The pore-forming agent is a substance dispersed in a polyolefin polymer and exhibiting a heterogeneity of a film produced through extrusion or the like, and is removed from the film at a later stage. Thus, the portion of the film where the pore-forming agent is located remains in the form of pores. The pore-forming agent is preferably a liquid material in the extrusion process, but may be a solid-state material.

The pore-forming agent may be an aliphatic hydrocarbon-based solvent such as liquid paraffin, paraffin oil, mineral oil or paraffin wax; Vegetable oils such as soybean oil, sunflower oil, rapeseed oil, palm oil, palm oil, coconut oil, corn oil, grape seed oil, cotton seed oil and the like; Or a plasticizer such as a dialkyl phthalate. In particular, the plasticizer is selected from the group consisting of di-2-ethylhexyl phthalate (DOP), di-butyl phthalate (DBP), di- isononyl phthalate Di-isodecyl phthalate (DIDP), butyl benzyl phthalate (BBP), and the like.

In one embodiment of the present invention, the content of the pore-forming agent is generally required to be high in order to improve the degree of pore (that is, porosity) of the film. However, The porosity of the porous separator may be improved, but it may adversely affect the mechanical strength of the resulting porous separator due to the lowering of the tensile strength of the film. Therefore, the content of the pore-forming agent required according to one aspect of the present invention can be appropriately controlled. Preferably, the content of the pore-forming agent ranges from 20 to 50 parts by weight based on 100 parts by weight of the sum of the polyolefin polymer and the pore-forming agent.

In step S2, the mixture formed in step S1 is hot-extruded to obtain an unoriented polyolefin-based film. During the extrusion process, it can be heated to form a single phase, which is carried out through an extruder, which may be a single or twin screw extruder. The heating temperature will vary depending on the kind of the polyolefin polymer used. Further, the extrusion temperature may be about 150 캜 to about 300 캜. If the extrusion temperature exceeds 300 캜, the formed extruded film may be deteriorated, which is undesirable.

In one specific embodiment of the present invention, after the extrusion process, a casting process may be performed. This casting process is carried out at a temperature of about 120 DEG C or less. Preferably, it can be carried out at a temperature of about 100 DEG C or less. In addition, the casting step may be a method of contacting with a cooling medium, or a method of contacting a refrigerant-cooled roll or press. The cooling roll is not particularly limited in its kind and form. Increasing the casting speed can be advantageous for increasing the crystallization speed. Further, for example, the temperature difference between the cooling roll and the die may be made small, which may be advantageous in increasing the degree of crystallization of the separation membrane and forming a uniform pore size.

(S3), annealing the unstretched film obtained in the step (S2) is annealed. The annealing process stabilizes the crystal structure of the porous separator.

The annealing process may be conducted at a temperature of about 100 to about 200 &lt; 0 &gt; C. During the annealing process, it may be carried out in an oven at about 100 to about 200 DEG C, preferably about 125 to about 140 DEG C for a retention time of about 1 to about 60 minutes, preferably about 1 to about 5 minutes. Thus, the extruded film formed by staying at a constant temperature has an increased degree of crystallinity, and such a crystallized portion is advantageous for forming a desired pore in the stretching process.

(S4), the stretched film is formed by uniaxially stretching the film annealed in the step (S3) in the longitudinal direction. The stretching process is carried out through a stretcher commonly used in the art. Non - limiting examples of such stretching machines include axial differential stretchers and the like. The film thus stretched can further be improved in mechanical strength.

In step (S5), the pore-former is removed from the film by using a solvent in the film stretched in step (S4), thereby forming a porous film having a plurality of pores.

Removal of the pore-former may be accomplished using a solvent. Specifically, the pore former present in the porous film is removed, for example, by extraction with a solvent in one or more extraction tanks and drying. In addition, through this removal, the space occupied by the pore former is formed into pores. The solvent which can be used in the present invention is not particularly limited and any solvent capable of extracting the pore forming agent used for extrusion can be used. Preferably, the solvent is methyl ethyl ketone, methylene chloride ), Hexane and the like are suitable. The extraction method can be used in combination with all common solvent extraction methods such as immersion method, solvent spray method, ultrasonic method and the like.

As described above, the porous separator according to the present invention has a small thickness due to inorganic particles uniformly dispersed in the film, and the structural strength of the separator is improved due to the high mechanical strength of the separator in the thickness direction. In addition, the separator has high thermal stability and excellent porosity due to the inorganic particles. Accordingly, the porous separator according to the present invention can be applied to an electrochemical device such as a secondary cell.

100 ... Membrane 200 ... cathode
201 ... The anode collector 202 ... The anode active material layer
300 ... The anode 301 ... Anode collector
302 ... The positive electrode active material layer

Claims (13)

Wherein the porous film contains a polyolefin-based polymer and a plurality of inorganic particles, and has a plurality of pores formed therein.
The method according to claim 1,
Wherein the inorganic particles comprise 50 to 90 parts by weight of a first inorganic particle and 10 to 50 parts by weight of a second inorganic particle, wherein the average particle diameter of the first inorganic particle is greater than the average particle diameter of the second inorganic particle Wherein the average particle size is less than the average particle size.
The method according to claim 1,
Wherein the polyolefin-based polymer resin is one or two or more polymers or copolymers selected from the group consisting of ethylene, propylene, 1-butene, 4-methyl-1-pentene, And mixtures thereof. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
The method according to claim 1,
Wherein the porous film comprises 10 to 30 parts by weight of inorganic particles relative to 100 parts by weight of the film.
The method according to claim 1,
Wherein the inorganic particles are inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transporting ability, or mixtures thereof.
6. The method of claim 5,
Wherein the inorganic particles having a dielectric constant of 5 or more are 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 0 <x <1, 0 < y <1), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, 0 <x <1), hafnia (HfO ₂ ) selected from the group consisting of SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ By weight of the porous separator.
The method according to claim 1,
Wherein the surface of the inorganic particles is modified with an organic polymer.
The method according to claim 1,
Wherein the porous separator has a thickness of 5 占 퐉 to 20 占 퐉. 3. The method of claim 2,
Wherein the first inorganic particles have an average particle diameter of 5 nm to 100 nm and the second inorganic particles have an average particle diameter of 100 nm or more and 1,000 nm or less.
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 porous separator of any one of claims 1 to 9.
(S1) preparing a mixture comprising a polymer resin, inorganic particles and a pore-forming agent;
(S2) a step (S2) of obtaining an unstretched film by extruding the mixture of (S1);
(S3) annealing the unstretched film of (S2);
(S4) stretching the unstretched film of (S3); And
(S5) removing the pore-forming agent to form a porous film;
Wherein the porous separator is a porous separator.
12. The method of claim 11,
Wherein the extrusion of (S1) is performed at a temperature of 150 to 300 캜.
12. The method of claim 11,
Wherein the inorganic particles include a first inorganic particle and a second inorganic particle, and the average particle diameter of the first inorganic particle is smaller than the average particle diameter of the second inorganic particle.

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