KR20170093606A - Separator and method for manufacturing thereof - Google Patents

Abstract

The present invention provides a separation membrane capable of decreasing electric resistance while preventing lowering of the conductivity of an electrode surface layer; and a manufacturing method thereof. According to the present invention, the separation membrane comprises: a porous polymer base; and a porous coating layer formed on at least part of the porous polymer base. The porous coating layer has inorganic particles with a conductive material coated on the surface thereof and a binder polymer. The conductive material is at least one selected from a group including carbon nanotube, carbon fiber, and graphite.

Description

[0001] SEPARATOR AND METHOD FOR MANUFACTURING THEREOF [0002]

The present invention relates to a separation membrane and a method of manufacturing the same, and more particularly, to a separation membrane having improved conductivity and minimized increase in electrode resistance and a method of manufacturing the same.

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. Electrochemical devices have attracted the greatest attention in this respect, among which the development of rechargeable secondary batteries capable of being charged and discharged has become a focus of attention. In recent years, in order to improve capacity density and specific energy in developing such batteries, Research and development on the design of new batteries is under way.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution .

The lithium secondary battery can be manufactured in various forms, and typical shapes include a cylindrical shape and a square shape, which are mainly used in a lithium ion battery. In recent years, a lithium polymer battery that is exposed to light is made of a material having flexibility, and its shape is relatively free. In addition, there is an advantage in that the portable electronic device is slim and light in weight because of its excellent safety and light weight.

The lithium secondary battery generally includes a positive electrode having a positive electrode active material layer formed on at least one surface of a positive electrode current collector, a negative electrode having a negative electrode active material layer formed on at least one surface of the negative electrode current collector and a negative electrode interposed between the positive electrode and the negative electrode, And a separator for insulation. As a method for forming the electrode (anode or cathode) active material layer on the current collector, the electrode active material slurry in which the electrode active material particles, the conductive material particles and the binder resin are dispersed in a solvent is directly applied to the current collector and dried, A slurry is coated on an upper portion of a separate support, followed by drying, and then the film separated from the support is laminated on the current collector.

The binder resin of the electrode in which the electrode active material layer is formed on one surface of the current collector according to the above-described conventional method connects the electrode active material particles to each other and fixes them to the current collector. The conductive material particles of a minute size are not dispersed in the binder resin, They physically make point contact with the electrode active material particles to serve as a conductive material.

However, when the battery is used for a long time, volume expansion of the electrode active material layer occurs, thereby causing a gap between the conductive material particles that have been in point contact with the electrode active material, There is a problem that the interaction between the particles and the electrode active material particles is weakened and the ion conductivity of the electrode is lowered.

When the electrode active material slurry is prepared and coated on the surface of the electrode current collector, the electrode active material having a high density of particles sinks toward the current collector, and the binder resin having a relatively low density moves toward the surface of the electrode. Is reduced.

In order to solve this problem, a method of increasing the content of the conductive material has been introduced, but the content of the electrode active material is relatively decreased and the capacity of the secondary battery is decreased.

Disclosure of Invention Technical Problem [8] The present invention provides a separator which can reduce electrical resistance while preventing conductivity of an electrode surface layer by using inorganic particles coated with a conductive material, and a method of manufacturing the same.

Other objects and advantages of the present invention will become apparent from the following description. It is also to be easily understood that other objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

According to an aspect of the present invention, there is provided a separation membrane comprising a porous polymer base material and a porous coating layer formed on at least one surface of the porous polymer base material, wherein the porous coating layer comprises inorganic particles And a binder polymer.

The conductive material may be at least one selected from the group consisting of carbon nanotubes, carbon fibers, and graphite.

The average diameter of the conductive material may be 10 to 500 nm.

The conductive material may be at least one of a rod shape, a tube shape, a disk shape, and a plate shape.

The specific surface area of the conductive material may be 90 to 300 m ² / g.

The content of the conductive material may be 5 to 30 parts by weight based on 100 parts by weight of the inorganic particles.

The inorganic particles may be any one of inorganic particles selected from inorganic particles having a dielectric constant of 5 or more and inorganic particles having lithium ion transferring ability, or a mixture of two or more thereof.

The inorganic particles is greater than or equal to the dielectric constant of _{5 BaTiO 3, Pb (ZrxTi1-} 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 ) Any one of inorganic particles 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 , Or a mixture of two or more of them.

Wherein the inorganic particles having lithium ion transferring ability are selected from the group consisting of lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x < (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 Mani Titanium (Li _x Ge _y P _z S _w, (Li _x N _y , 0 <x <4, 0 <y <2), SiS ₂ (0 <x <4, 0 <y <1, 0 <z < 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 < z < 7) series glass.

The binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-cohexafluoropropylene, polyvinylidene fluoridecotrichloroethylene, polymethylmethacrylate, polybutylacrylate ), Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, ), One selected from the group consisting of cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or two of them Or more.

According to another aspect of the present invention, there is provided an electrode comprising an electrode active material layer formed on at least one surface of a separator, an electrode current collector, and an electrode current collector, There is provided a secondary battery in which a coating layer and an electrode active material layer of the electrode face each other.

The secondary battery may be a lithium ion secondary battery.

According to another aspect of the present invention, there is provided a method for manufacturing a conductive particle, comprising the steps of: adding inorganic particles to a coating liquid in which a conductive material and a dispersing material are mixed to obtain inorganic particles coated with a conductive material on the surface; Coating a surface of the porous polymer substrate with inorganic particles coated with a conductive material, a binder and a solvent to prepare a porous coating layer slurry, coating the porous coating layer slurry on at least one surface of the porous polymer substrate, and removing the solvent of the porous coating layer slurry A method for producing a separation membrane comprising the steps of:

The dispersant may be 5 to 20 parts by weight based on 100 parts by weight of the conductive material.

According to another aspect of the present invention, there is provided a separation membrane produced by the above-described method and a secondary battery including the same.

The present invention uses a separation membrane containing inorganic particles coated with a conductive material to prevent a decrease in conductivity of the electrode surface and has an advantage of reducing electrical resistance.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and, together with the description of the invention, It is not interpreted.
1 is a cross-sectional view schematically showing a cross section of a separation membrane including a conventional porous coating layer.
2 is a cross-sectional view schematically showing a cross-section of a separation membrane according to an embodiment of the present invention.
Figs. 3 and 4 are SEM photographs of carbon nanotubes of Example 1. Fig.
5 is a flow chart of a method of manufacturing a separation membrane according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary terms, and the inventor should properly define the concept of the term to describe its own invention as the best invention It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, 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 are not intended to represent all of the technical ideas of the present invention. Therefore, It should be understood that various equivalents and modifications are possible.

FIG. 1 is a cross-sectional view schematically showing a cross-section of a separation membrane including a conventional porous coating layer, and FIG. 2 is a cross-sectional view schematically showing a cross-section of a separation membrane according to an embodiment of the present invention.

2, in accordance with a preferred embodiment of the present invention, a separation membrane comprising a porous polymer substrate 10 and a porous coating layer formed on at least one surface of the porous polymer substrate, the porous coating layer comprising a conductive material 22 ) Coated with inorganic particles 21 and a binder polymer are provided.

The porous polymer base material applicable to the present invention may be a porous polymeric film base or a porous polymer nonwoven base base.

The porous polymeric film substrate may be a porous polymeric film made of a polyolefin such as polyethylene or polypropylene. The polyolefin porous polymeric film substrate exhibits a shutdown function at a temperature of, for example, 80 to 130 ° C.

At this time, the polyolefin porous polymer film may be made of a polyolefin-based polymer such as polyethylene, polypropylene, polybutylene or polypentene such as high density polyethylene, linear low density polyethylene, low density polyethylene, ultra high molecular weight polyethylene, .

In addition, the porous polymeric film substrate may be produced by molding various polymeric materials such as polyester in addition to polyolefin. In addition, the porous polymeric film substrate may have a structure in which two or more film layers are laminated, and each film layer may be formed of a polymer such as polyolefin, polyester, or the like, It is possible.

In addition, the porous polymer film base and the porous nonwoven base material may be formed of a material selected from the group consisting of polyethyleneterephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, Polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfide, polyethylenenaphthalene, polyetherketone, polyetherketone, polyetherketone, And the like may be used alone or in the form of a mixture thereof.

The porous coating layer may be formed on one side or both sides of the porous polymer substrate. According to a preferred embodiment, the porous coating includes inorganic particles and a binder coated on the surface of the porous polymer substrate.

The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as oxidation and / or reduction reaction does not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ). 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.

For the reasons stated above, the inorganic particles may include high-permittivity inorganic particles having a dielectric constant of 5 or more, or 10 or more, inorganic particles having lithium ion-transporting ability, or a mixture thereof.

Nonlimiting examples of 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 -xPbTiO 3 (PMN-PT, 0 <x <1), Wherein the metal oxide selected from the group consisting of 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 TiO ₂ Inorganic particles such as one or a mixture of two or more of them exhibit high dielectric constant characteristics with a dielectric constant of 100 or more, but also piezoelectricity in which electric charges are generated when a certain pressure is applied and tensile or compressed, It is possible to prevent internal short-circuiting of both electrodes due to an external impact, thereby improving the safety of the electrochemical device.

As the inorganic particles, inorganic particles having a lithium ion transferring ability, that is, inorganic particles containing a lithium element but having a function of transferring lithium ions without storing lithium can be used. Non-limiting examples of inorganic particles having lithium ion transferring ability include 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), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), Li (LiAlTiP) _x O _y series glass (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5) such as _3.25 Ge _0.25 P _0.75 S ₄ , (Li _x N _y , 0 <x <4, 0 <y <2) such as Li ₃ N and Li ₃ PO ₄ -Li ₂ S-SiS ₂ SiS ₂ family, such as _{glass (Li x Si y S z} , 0 <x <3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 (Li _x P _y S _z , 0 <x <3, 0 <y <3, 0 <z <7) such as P ₂ S ₅ series glass or mixtures thereof, When the inorganic particles having ion transport ability are mixed, their synergistic effect can be doubled.

The inorganic particles may be coated with a conductive material on the surface. As a result, when the electrode slurry is generally prepared and coated on the surface of the electrode collector, the electrode active material having a high density of particles sinks toward the collector and the binder having a relatively low density moves to the electrode surface, And the porous coating layer including inorganic particles coated with a conductive material as described above is included in the separation membrane that forms an interface with the anode and the cathode so that the conductivity of the electrode surface which has been reduced due to the movement of the binder Can be reinforced.

The conductive material may be any material having conductivity in the electrochemical device without any reaction with the inorganic particles, and may be used without limitation. Preferably, the material is at least one selected from the group consisting of carbon nanotubes, carbon fibers and graphite, May be carbon nanotubes .

Generally, the isolation function is most important. However, in the case of the binder polymer used in the porous coating layer, there is a problem of increasing the electrode resistance. However, by using the conductive material described above, the increase in resistance due to the binder polymer can be solved.

The average diameter of the conductive material is in the range of 10 to 500 nm, preferably 10 to 100 nm. If the conductive material is thinner than the above range, the specific surface area becomes very large. If the particles are aggregated due to the attractive force between the particles, If the thickness is larger than the above range, the thickness of the coating layer of the separator becomes similar to that of the coating layer of the separator, and there is a problem that the conductive layer is rubbed and tangled due to the raising and breaking of the fabric. .

The conductive material may be at least one of a rod shape, a tube shape, a disk shape, and a plate shape, preferably a rod shape.

The specific surface area of the conductive material is in the range of 90 to 300 m ² / g. When the conductive material exceeds the above range, the conductive material agglomerates due to the cohesive force of the particles.

Also, the content of the conductive material is 5 to 30 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the inorganic particles. If the content of the conductive material is lower than 5, the effect of reducing the binder resistance is not obtained. If the content of the conductive material is higher than 30, dispersion stability is generated. Also, excessive conductive material may clog the membrane pores, The possibility of the separation membrane itself arises.

The binder polymer that can be used in the present invention may be at least one selected from the group consisting of polyvinylidene fluoride-cohexafluoropropylene, polyvinylidene fluoridecotrichloroethylene, polymethylmethacrylate, Polybutylene terephthalate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide (polyethylene) oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolylane, Vinyl al a polymer selected from the group consisting of cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or a polymer selected from the group consisting of Or a mixture of two or more thereof.

The binder polymer applicable to the present invention is preferably a polymer having a glass transition temperature (T _g ) of -200 to 200 ° C, which is a mechanical property such as flexibility and elasticity of a finally formed porous coating layer. It is possible to improve the physical properties.

In the porous coating layer, the inorganic particles are charged and bound to each other by the binder polymer fibers in contact with each other, thereby forming an interstitial volume between the inorganic particles, The interstitial volume becomes void and forms pores.

That is, the binder polymer fibers attach the inorganic particles to each other so that the inorganic particles can remain bonded to each other. For example, the binder polymer fibers connect and fix the inorganic particles. In addition, the pores of the porous coating layer are pores formed by interstitial volume between inorganic particles as void spaces, and the pores of the porous coating layer are formed of inorganic materials substantially closed in a packed structure (closed packed or densely packed) It is the space defined by the particles. A path through which lithium ions necessary for operating the battery through the pores of the porous coating layer can be provided.

The weight ratio of the inorganic particles contained in the porous coating layer to the binder polymer fibers is in the range of 50:50 to 99: 1, and preferably 70:30 to 95: 5. When the inorganic material content ratio of the binder polymer fibers is less than 50:50, improvement of the thermal stability of the separator is deteriorated due to an increase of the polymer content and interstitial volume formed between the inorganic particles is not sufficiently formed, There is a problem that the pore size and porosity decrease. When the content of the inorganic particles exceeds 99 parts by weight, there is a problem that the fillerability of the porous coating layer is weakened because the content of the binder polymer is relatively small.

The separator of the present invention may further comprise other additives in addition to the above-mentioned binder polymer fibers and inorganic particles as the porous coating layer component.

According to another aspect of the present invention, there is provided a separator comprising an electrode including the separator, the electrode collector, and an electrode active material layer formed on at least one surface of the electrode collector, wherein the porous coating layer of the separator and the active material layer of the electrode face each other A secondary battery is provided.

The electrode current collector may be a positive electrode current collector or a negative electrode current collector. Non-limiting examples of the positive electrode current collector include carbon, nickel, titanium, and aluminum on the surface of stainless steel, aluminum, nickel, titanium, Or the like may be used. Non-limiting examples of the anode current collector include copper; Stainless steel; aluminum; nickel; titanium; Fired carbon; Stainless steel surface-treated with copper, carbon, nickel, titanium or silver; aluminum-cadmium alloy;

The electrode active material layer may be a positive active material layer or a negative active material layer.

At this time, the cathode active material layer may include a cathode active material, and the anode active material layer may include a cathode active material.

The positive electrode active material is _{LiCoO 2, LiNiO 2, LiMn 2} O 4, LiCoPO 4, LiFePO 4, LiNiMnCoO 2 , and _{LiNi 1-x- yz Co x M1} y M2 z O 2 (M1 and M2 are independently selected from Al, Ni each other, X, y and z are independently selected from the group consisting of Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, 0? Y? 0.5, 0? Z <0.5, 0 <x + y + z? 1).

The negative electrode active material may be at least one selected from the group consisting of natural graphite, artificial graphite, a carbonaceous material, lithium-containing titanium composite oxide (LTO), metals (Me) with Si, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; An alloy composed of the metal (Me); An oxide of the metal (Me) (MeOx); And a composite of the metal (Me) and carbon, and the like.

The electrode active material layer forms an electrode active material layer on the current collector by using an electrode composition including a binder, a solvent, and a conductive material in addition to the electrode active material. At this time, the method of forming the electrode active material layer may be a method of directly coating the electrode active material composition on the collector, or a method of coating the electrode active material composition on a separate support and drying, As shown in FIG. Here, the support may be any as long as it can support the active material layer. Specific examples thereof include a mylar film, a polyethylene terephthalate (PET) film, and the like.

The binder, conductive material, and solvent may be those conventionally used in the production of lithium secondary batteries.

Specifically, the binder may include vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate ) And mixtures thereof can be used. Examples of the conductive material include carbon black or acetylene black, and examples of the solvent include acetone and N-methylpyrrolidone.

At this time, the secondary battery may be a lithium ion secondary battery.

FIG. 5 is a flowchart illustrating a method of manufacturing a separation membrane according to another embodiment of the present invention. Referring to FIG. 5, a separation membrane manufacturing method according to an embodiment of the present invention includes the steps of: A step S200 of preparing a porous coating layer slurry, a step S300 of coating a porous coating layer slurry, and a step S400 of removing a solvent of the porous coating layer slurry.

The step (S100) of obtaining the inorganic particles coated with the conductive material on the surface is a step of spraying the inorganic material particles with the coating solution containing the conductive material and the dispersing agent to obtain the inorganic particles coated with the conductive material on the surface.

Specifically, if the coating liquid mixed with the conductive material and the dispersing material and the inorganic material are mixed with strong stirring, they can be adsorbed on the surfaces of the inorganic particles, which are particles larger than the conductive material.

At this time, the dispersing material can be used without limitation in the technical field. For example, PVP, PVA, rubber dispersing agent and the like can be used.

The dispersion material may be 5 to 20 parts by weight, preferably 5 to 10 parts by weight based on 100 parts by weight of the binder. If the dispersion material is out of the range, conductive material aggregates are produced due to the dispersion property of the conductive material, Or stability.

The step S200 of preparing the porous coating layer slurry is a step of preparing a porous coating layer slurry by mixing inorganic particles coated with a conductive agent on the surface, a binder and a solvent.

It is preferable that the solvent does not dissolve the binder polymer fiber to be used and has a low boiling point. This is to maintain the fiber form to prevent penetration into the pores of the substrate and then to facilitate solvent removal, and non-limiting examples of solvents that can be used include acetone, tetrahydrofuran, methylene chloride ( methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water or a mixture thereof .

The step S300 of coating the porous coating layer slurry is a step of coating the porous coating layer slurry on at least one surface of the porous polymer substrate, and may be selectively coated on both sides or only one side of the porous polymer substrate.

In this case, the coating method can be used without limitation including coating methods commonly used in the art, including but not limited to dip coating, die coating, roll coating, comma coating, Or a combination thereof may be used.

The step of removing the solvent of the porous coating layer slurry (S300) is a step of removing the solvent of the slurry by heating and drying, and the heating temperature may be variously applied depending on the solvent used.

According to another embodiment of the present invention, a separator manufactured by the above-described method and a secondary battery including the separator may be provided.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention in a person having average knowledge in the art.

[Example 1] Production of organic-based membrane

15 g of conductive material and 50 g of acetone are added to 12.5 g of a dispersant solution prepared from 8% acetone solution and dispersed using ball-mill equipment to prepare a conductive material / dispersant slurry. When 20 g of inorganic particles and 232 g of Acetone are added to the prepared 15 wt% conductive material / dispersant slurry and dispersed using ball-mill equipment, a 20 wt% slurry of conductive material / inorganic material / dispersant can be prepared. Using this method, a membrane is prepared by using a dip coating method.

[Example 2]

20 g of conductive material and 57 g of Di-water were added to 37.5 g of the dispersant solution prepared in 8% solution and dispersed using ball-mill equipment to prepare a conductive material / dispersant slurry. 100 g of inorganic particles and 377 g of Acetone were added to the prepared 20 wt% conductive material / dispersant slurry and dispersed using a ball-mill apparatus to prepare a 25 wt% slurry of a conductive material / inorganic material / dispersant. Using this method, a membrane is prepared by using a dip coating method.

[Comparative Example 1]

100 g of inorganic material, 210 g of acetone, and 20 g of organic binder were added and dispersed using a ball-mill apparatus to prepare an inorganic slurry of about 30 wt%. Using this method, a membrane is prepared by using a dip coating method.

[Comparative Example 2]

100 g of inorganic material, 120 g of water, and 30 g of CMC / SBR are placed and dispersed using a ball-mill apparatus to prepare an inorganic slurry of about 40 wt%. Using this, a double-dip coating method is used to produce a membrane.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

1: Membrane
10: Porous polymer substrate
20: inorganic particles
21: Conductive material-coated inorganic particles
22: Conductive material

Claims (16)

A separation membrane comprising a porous polymer base material and a porous coating layer formed on at least one surface of the porous polymer base material,
Wherein the porous coating layer comprises inorganic particles coated with a conductive material on a surface thereof and a binder polymer. The method according to claim 1,
Wherein the conductive material is at least one selected from the group consisting of carbon nanotubes, carbon fibers, and graphite. The method according to claim 1,
Wherein the conductive material has an average diameter of 10 to 500 nm. The method according to claim 1,
Wherein the conductive material is at least one of a rod shape, a tube shape, a disk shape, and a plate shape. The method according to claim 1,
Wherein the conductive material has a specific surface area of 90 to 300 m ² / g. The method according to claim 1,
Wherein a content of the conductive material is 5 to 30 parts by weight based on 100 parts by weight of the inorganic particles. The method according to claim 1,
Wherein the inorganic particles are inorganic particles selected from inorganic particles having a dielectric constant of 5 or more and inorganic particles having a lithium ion transporting ability, or a mixture of two or more thereof. The method according to claim 1,
The inorganic particles is greater than or equal to the dielectric constant of _{5 BaTiO 3, Pb (ZrxTi1-} 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 ) Any one of inorganic particles 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 , Or a mixture of two or more thereof. The method according to claim 1,
Wherein the inorganic particles having lithium ion transferring ability are selected from the group consisting of lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x < (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 Mani Titanium (Li _x Ge _y P _z S _w, (Li _x N _y , 0 <x <4, 0 <y <2), SiS ₂ (0 <x <4, 0 <y <1, 0 <z < 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 < z < 7) series glass. The method according to claim 1,
The binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-cohexafluoropropylene, polyvinylidene fluoridecotrichloroethylene, polymethylmethacrylate, polybutylacrylate ), Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinyl,
A polymer selected from the group consisting of cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan and carboxyl methyl cellulose, or a mixture thereof. Wherein the membrane is formed of a mixture of two or more of the above. 12. A separator according to any one of claims 1 to 11, And
An electrode current collector, and an electrode active material layer formed on at least one surface of the electrode current collector,
Wherein the porous coating layer of the separation membrane and the electrode active material layer of the electrode face each other. 13. The method of claim 12,
Wherein the secondary battery is a lithium ion secondary battery. Adding a conductive material and a dispersing agent to a coating liquid mixed with inorganic particles to obtain inorganic particles coated with a conductive material on the surface;
Mixing the surface with inorganic particles coated with a conductive material, a binder and a solvent to prepare a porous coating layer slurry;
Coating the porous coating layer slurry on at least one surface of the porous polymeric substrate; And
And removing the solvent of the porous coating layer slurry. 14. The method of claim 13,
Wherein the dispersion material is 5 to 20 parts by weight based on 100 parts by weight of the conductive material. 17. A membrane produced by the method of any one of claims 13 to 16. A secondary battery comprising the separator of claim 15.

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