KR101708882B1 - Preparation method of separator - Google Patents

Abstract

A separator manufacturing method of the present invention comprises the steps of: (S1) preparing a porous substrate having pores; (S2) coating the nonwoven fabric on at least one surface of the porous substrate; (S3) coating a slurry on which the inorganic particles are dispersed and in which the binder polymer is dissolved in the solvent, on the coated non-solvent; And (S4) simultaneously drying the non-solvent and the solvent to form porous organic-inorganic complexes containing pores formed due to the interstitial volume between the inorganic particles while the inorganic particles are connected and fixed to each other by the binder polymer Thereby forming a layer on the porous substrate. According to the production method of the present invention, the phenomenon that the pores of the porous base material are clogged by the binder polymer in the slurry can be minimized, so that the increase in the resistance of the separator due to the formation of the porous organic-inorganic composite layer can be reduced.

Description

PREPARATION METHOD OF SEPARATOR [0002]

The present invention relates to a method for producing a separator of an electrochemical device such as a lithium secondary battery, and more particularly, to a separator having a porous organic-inorganic hybrid layer containing a mixture of inorganic particles and a binder polymer, And a manufacturing method thereof.

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 has become a focus of attention. In recent years, in order to improve the capacity density and specific energy in developing such batteries, And research and development on the design of the battery.

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 . However, such a lithium ion battery has safety problems such as ignition and explosion when using an organic electrolytic solution, and it is disadvantageous in that it is difficult to manufacture. Recently, the lithium ion polymer battery is considered to be one of the next generation batteries by improving the weak point of the lithium ion battery. However, since the capacity of the battery is still relatively low as compared with the lithium ion battery, Is urgently required.

Such electrochemical devices are produced in many companies, but their safety characteristics are different. It is very important to evaluate the safety and safety of such an electrochemical device. The most important consideration is that the electrochemical device should not injure the user in case of malfunction. For this purpose, the safety standard strictly regulates the ignition and fuming in the electrochemical device. In the safety characteristics of the electrochemical device, there is a high possibility that the electrochemical device is overheated and thermal explosion occurs or an explosion occurs when the separator is penetrated. Particularly, a polyolefin porous film commonly used as a separator of an electrochemical device exhibits extreme heat shrinkage behavior at a temperature of 100 DEG C or more owing to the characteristics of the manufacturing process including material properties and elongation, so that a short circuit between the anode and the cathode There is a problem causing it.

In order to solve the safety problem of such an electrochemical device, a separator has been proposed in which a porous organic-inorganic composite coating layer is formed by coating a mixture of inorganic particles and a binder polymer on at least one surface of a porous substrate having a plurality of pores. For example, in Korean Patent Publication No. 2007-0019958, a slurry in which inorganic particles are dispersed on a porous substrate and a binder polymer is dissolved in a solvent is coated on a porous substrate such as a polyolefin film and dried to form a porous organic- A manufacturing method for a separator provided on a porous substrate is disclosed.

In the separator in which the organic-inorganic composite porous coating layer is formed, the inorganic particles present in the porous coating layer formed on the porous substrate serve as a kind of spacer capable of maintaining the physical form of the porous coating layer, Thereby preventing shorting of both electrodes when thermal runaway occurs. In addition, interstitial volumes exist between the inorganic particles to form micropores.

Although the organic-inorganic composite porous coating layer contributes to the thermal stability of the separator, when the organic-inorganic composite porous coating layer is formed, the binder polymer flows into the pores of the porous substrate to block a part of the pores, .

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of manufacturing a separator capable of minimizing the clogging of pores of a porous substrate by a binder polymer when the organic-inorganic composite porous coating layer is formed, And an electrochemical device having the same.

In order to achieve the above object, the present invention provides a separator manufacturing method comprising:

(S1) preparing a porous substrate having pores;

(S2) coating the nonwoven fabric on at least one surface of the porous substrate;

(S3) coating a slurry on which the inorganic particles are dispersed and in which the binder polymer is dissolved in the solvent, on the coated non-solvent; And

(S4) The non-solvent and the solvent are simultaneously dried, and the inorganic particles are connected and fixed to each other by the binder polymer, so that the porous organic-inorganic composite layer containing pores formed by the interstitial volume between the inorganic particles So as to form on the porous substrate.

In the separator manufacturing method of the present invention, the porous substrate is preferably a polyolefin-based porous film, and the thickness of the porous substrate is preferably 1 to 100 μm.

In the separator manufacturing method of the present invention, the solubility index of the binder polymer is preferably 15 to 45 MPa ^1/2 . Examples of such a binder polymer include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, Polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide (polyvinylpyrrolidone), polyvinylacetate polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpyrrolidone, Ethyl polyvinyl alcohol (cyanoethylpo lyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan and carboxyl methyl cellulose may be used singly or in combination of two or more thereof. have.

In the separator manufacturing method of the present invention, the difference between the solubility index of the binder polymer and the non-solvent is preferably 5.5 Mpa ^1/2 or more, and the difference between the solubility index of the binder polymer and the solvent is preferably 5.0 Mpa ^1/2 or less. Non-solvents include water, methanol, ethanol, ethylene glycol, glycerol And the like can be used alone or in combination of two or more thereof. Examples of the solvent include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide N-methyl-2-pyrrolidone (NMP), cyclohexane, and the like, or two or more of them may be used in combination.

In the separator manufacturing method of the present invention, the average particle diameter of the inorganic particles is preferably 0.001 to 10 탆, and the weight ratio of the inorganic particles to the binder polymer is preferably 50: 50 to 99: 1.

In the separator manufacturing method of the present invention, the coating thickness of the non-solvent is preferably 5 to 250 μm, and the coating thickness of the slurry is preferably such that the thickness of the porous organic-inorganic composite layer finally formed after drying is 0.1 to 20 μm .

The separator of the present invention manufactured by such a method can be interposed between a cathode and an anode to produce an electrochemical device such as a lithium secondary battery or a supercapacitor.

The separator produced according to the method of the present invention exhibits the following characteristics.

First, when the electrochemical device is overheated, the porous organic-inorganic composite layer suppresses heat shrinkage of the porous substrate and prevents shorting of both electrodes when thermal runaway occurs.

Second, when the organic-inorganic composite porous coating layer is formed, the phenomenon that the binder polymer in the slurry flows into the pores of the porous substrate is improved, and thus the phenomenon of clogging of the pores of the porous substrate is minimized. As a result, the increase in the resistance of the separator due to the formation of the porous organic-inorganic hybrid layer is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a method of manufacturing a separator according to an embodiment of the present invention; FIG.

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 should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the constitutions described in the embodiments described herein 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, various equivalents which can be substituted at the time of application It should be understood that variations can be made.

The method of manufacturing the separator of the present invention will be described in detail as follows.

First, a porous substrate having pores is prepared (step S1).

As such a porous substrate, any porous substrate commonly used in an electrochemical device such as a porous membrane or a nonwoven fabric formed of various polymers can be used. For example, a polyolefin porous film used as a separator of an electrochemical device, particularly, a lithium secondary battery, or a nonwoven fabric made of polyethylene terephthalate fiber may be used. The material and the shape may be variously selected depending on the purpose. For example, the polyolefin-based porous membrane 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, And the nonwoven fabric may be made of a polyolefin-based polymer or a fiber using a polymer having higher heat resistance. The thickness of the porous substrate is not particularly limited, but is preferably 1 to 100 占 퐉, more preferably 5 to 50 占 퐉, and the pore size and porosity present in the porous substrate are also not particularly limited, but 0.001 to 50 占 퐉 and 10 To 95%.

Next, the nonwoven fabric is coated on at least one surface of the porous substrate (step S2).

In the present invention, the non-solvent means a non-solvent for the binder polymer described later. It is preferable to use a binder polymer having a solubility index difference of 5.5 Mpa ^1/2 or more with respect to the binder polymer. Water, methanol, ethanol, ethylene glycol, glycerol and the like may be used alone or in combination of two or more thereof as the non-solvent.

The coating thickness of the non-solvent is preferably 5 to 250 占 퐉 in consideration of the effect of the non-solvent coating and the efficiency depending on the drying speed.

Then, a slurry in which the inorganic particles are dispersed and the binder polymer is dissolved in the solvent is coated on the coated non-solvent (step S3).

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, it is preferable that the inorganic particles include high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more. Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT, Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO , NiO, CaO, ZnO, ZrO 2, Y 2 O 3, Al 2 O 3, TiO 2, SiC Or a mixture thereof.

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, including (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) (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5) such as Li _3.25 Ge _0.25 P _0.75 S ₄ ), Li ₃ lithium nitride such as _{N (Li x N y, 0} <x <4, 0 <y <2), Li 3 PO 4 SiS 2 family, such as _{-Li 2 S-SiS 2 glass (} Li x Si _{y S z, 0 <x <} 3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 , etc., such as P ₂ S ₅ based _{glass (Li x P y S z} , 0 <x <3, 0 <y <3, 0 <z <7), or a mixture thereof.

The average particle diameter of the inorganic particles is not particularly limited, but is preferably in the range of 0.001 to 10 mu m for the formation of the coating layer of uniform thickness and the adequate porosity. If it is less than 0.001 mu m, the dispersibility may be deteriorated, and if it exceeds 10 mu m, the thickness of the formed coating layer may increase.

The binder polymer is preferably a polymer having a glass transition temperature (T _g ) of -200 to 200 ° C because it can improve the mechanical properties such as flexibility and elasticity of the coating layer finally formed .

In addition, the binder polymer does not necessarily have ion conductivity, but the performance of the electrochemical device can be further improved by using a polymer having ion conductivity. Therefore, it is preferable that the binder polymer has a high permittivity constant. In fact, since the dissociation degree of the salt in the electrolyte depends on the permittivity constant of the electrolyte solvent, the higher the permittivity constant of the binder polymer, the better the salt dissociation in the electrolyte. The dielectric constant of such a binder polymer may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), preferably 10 or more.

In addition to the functions described above, the binder polymer may be characterized by being capable of exhibiting a high degree of swelling of the electrolyte by being gelled upon impregnation with a liquid electrolyte. Accordingly, it is preferable to use a polymer having a solubility index of 15 to 45 MPa ^1/2 , more preferably a solubility index of 15 to 25 MPa ^1/2 and a range of 30 to 45 MPa ^1/2 . Therefore, it is preferable to use hydrophilic polymers having many polar groups, rather than hydrophobic polymers such as polyolefins. If the solubility index is less than 15 MPa &lt; ^1/2 &gt; and more than 45 MPa &lt; ^1/2 &gt;, it is difficult to swell by a conventional liquid electrolyte for a battery.

Non-limiting examples of such a binder polymer include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, But are not limited to, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, Polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, and the like. ), Cyanoethylpolybio Cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, and the like can be mentioned. These may be used alone or in combination of two or more thereof. Two or more species may be used in combination.

The weight ratio of the inorganic particles to the binder polymer is preferably in the range of, for example, 50:50 to 99: 1, more preferably 70:30 to 95: 5. When the content ratio of the inorganic particles to the binder polymer is less than 50:50, the content of the polymer is increased and the pore size and porosity of the formed coating layer can be reduced. If the content of the inorganic particles exceeds 99 parts by weight, the fillerability of the formed coating layer may be weakened because the content of the binder polymer is small.

In the present invention, the solvent means a liquid capable of dissolving the binder polymer. As the solvent of the binder polymer, it is preferable that the solubility index is similar to that of the binder polymer to be used, and the boiling point is low. This is to facilitate uniform mixing and subsequent solvent removal. Further, it is preferable that the boiling point of the solvent is equal to or lower than that of the non-solvent. This is because, in the drying process described later, it is preferable that the solvent is dried simultaneously with the non-solvent or the solvent is dried at a rate faster than the non-solvent.

Non-limiting examples of usable solvents include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone ( N-methyl-2-pyrrolidone, NMP), cyclohexane, or a mixture thereof.

In the separator manufacturing method of the present invention, it is preferable that the mutual solubility index difference between the binder polymer and the solvent is 5 Mpa ^1/2 or less in consideration of ease of slurry coating and prevention of gelation of the binder polymer in the slurry.

The slurry in which the inorganic particles are dispersed and the binder polymer is dissolved in the solvent can be prepared by dissolving the binder polymer in a solvent and then adding and dispersing the inorganic particles, but the present invention is not limited thereto. The inorganic particles may be added in a state of being crushed to an appropriate size, but it is preferable to disperse the inorganic particles after crushing the inorganic particles after adding the inorganic particles to the solution of the binder polymer.

The coating thickness of the slurry coated on the porous substrate is preferably adjusted so that the thickness of the porous organic-inorganic composite layer finally formed after drying is 0.1 to 20 탆 in consideration of the over-resistance of the improvement of stability of the battery.

The coating of the non-solvent according to the step (S2) and the coating of the slurry according to the step (S3) may be continuously or discontinuously performed using various methods such as slot die coating, slide coating, curtain coating and the like. In particular, in terms of productivity, it is preferable that the coatings of (S2) and (S3) are carried out continuously or simultaneously, and the most preferred example is shown in FIG.

Referring to FIG. 1, a die 1 having two slots 3a, 3b is used to perform the coating of the non-solvent according to (S2) and the coating of the slurry according to (S3). And the non-solvent 7 is supplied through the first slot 3a. Further, the slurry 5 in which the inorganic particles are dispersed and the binder polymer is dissolved in the solvent is supplied through the second slot 3b. When the porous substrate 9 is supplied to the rotating roller, the non-solvent 7 is coated on the porous substrate 9, and the slurry 5 is coated on the non-solvent 7 continuously.

Finally, the non-solvent coated on the porous substrate and the solvent present in the slurry are simultaneously dried to form pores formed due to the interstitial volume between the inorganic particles while the inorganic particles are connected and fixed to each other by the binder polymer Inorganic composite layer is formed on the porous substrate (step S4).

The characteristics of the porous organic-inorganic hybrid layer formed according to the production method of the present invention will be described below.

(S3) The result is a structure in which a non-porous film is coated on a porous substrate, and a slurry is coated thereon. The non-porous layer serves as a kind of barrier layer that minimizes the contact of the binder polymer dissolved in the slurry with the porous substrate. In addition, it is presumed that some of the binder polymer diffused into the nonwoven fabric layer will be gelated or precipitated by the nonwoven fabric to become difficult to enter the pores of the porous base material.

(S3) When the resultant is passed through a dryer, the slurry coated on the non-solvent is first subjected to heat or hot air. Thus, the solvent in the slurry coated on the outer portion is dried at a rate faster than the non-solvent. Thus, before the non-solvent coating layer is completely dried, pores are formed due to the interstitial volume between the inorganic particles, while the inorganic particles existing in the outermost portion of the slurry coating layer are connected and fixed to each other by the binder polymer . That is, due to the coated non-porous layer, diffusion of the binder polymer in the slurry into the pores of the porous substrate during drying is minimized. As a result, the phenomenon that the pores of the porous substrate are clogged by the binder polymer in the slurry is minimized, thereby improving the problem of increasing the resistance of the separator due to the formation of the porous organic-inorganic composite layer.

The porous organic-inorganic composite layer, which has been formed on the porous substrate through the above-described processes, is formed such that the binder polymer adheres to each other (that is, the binder polymer connects and fixes the inorganic particles between the inorganic particles) And the porous organic-inorganic hybrid layer remains bonded to the porous substrate by the binder polymer. The inorganic particles of the porous organic-inorganic hybrid layer exist in a densely packed structure in contact with each other, and the interstitial volume generated when the inorganic particles are in contact becomes the pores of the porous organic-inorganic hybrid layer.

The separator manufactured according to the above-described method can be manufactured by interposing, for example, winding or laminating between the positive electrode and the negative electrode. The electrochemical device includes all devices that perform an electrochemical reaction, and specific examples include capacitors such as all kinds of primary, secondary cells, fuel cells, solar cells, 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 current collector include aluminum, nickel, or a combination thereof. Examples of the negative current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

The electrolytic solution which can be used in the electrochemical device of the present invention is a salt having a structure such as A ⁺ B ^- , wherein A ⁺ includes an alkali metal cation such as Li ⁺ , Na ⁺ , K ^{+ -} it is _{^{PF 6 -, BF 4 -,}} Cl -, Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF ₂ SO _{2) 3} ^- anion, or a salt containing an ion composed of a combination of propylene carbonate (PC) such as, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl (DMP), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma-butyrolactone Or an organic solvent composed of a mixture thereof, but the present invention is not limited thereto.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

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. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example 1

PVdF-CTFE (polyvinylidene fluoride-chlorotrifluoroethylene copolymer) and Cyanoethylpullulan (cyanoethylpullulan) were added to acetone at a weight ratio of 10: 2, respectively, and dissolved at 50 DEG C for about 12 hours or longer to obtain a polymer solution . Al ₂ O ₃ powder and BaTiO ₃ powder in a weight ratio of 9: 1 were added to a polymer solution prepared so as to have a polymer / inorganic particle = 10/90 weight ratio, and the mixture was ball milled for 12 hours or longer The inorganic particles were crushed and dispersed to prepare a slurry. The average particle size of the inorganic particles of the thus prepared slurry was 600 nm on average.

Separately prepared methanol and the prepared slurry were continuously coated on one surface of a 12 占 퐉 thick polyethylene porous film (porosity of 45%) through the slot die shown in Fig. The coating thickness of the methanol was 10 탆, and the coating amount of the slurry was set to 60 탆 so that the thickness of the finally formed porous organic-inorganic hybrid layer was 4 탆.

Subsequently, the coated substrate was passed through a drier adjusted to a temperature of 50 DEG C to dry the non-solvent and the solvent to complete the separator.

The Gurley value of the finished separator was good at 205 sec / 100 mL. The resistance of the separator was 0.7 Ω, which was a good level.

Comparative Example 1

A separator was completed in the same manner as in Example 1, except that methanol was not coated and only the slurry was coated through the slot die shown in Fig. The coating amount of the slurry was adjusted so that the thickness of the finally formed porous organic-inorganic composite layer was 4 탆.

The Gurley value of the completed separator was 230 sec / 100 mL, and the resistance of the separator was increased to 1.0 Ω.

Comparative Example 2

The separator was completed in the same manner as in Comparative Example 1, except that the slurry was coated on both surfaces of the polyethylene porous film by a dip coating method instead of the slot die coating. The amount of the slurry coated on both sides was adjusted so that the thickness of the finally formed porous organic-inorganic composite layer was 2 탆 (sum of both side thicknesses was 4 탆).

The Gurley value of the completed separator was 290 sec / 100 mL, and the resistance of the separator was increased to 1.4 Ω.

The separators of Examples and Comparative Examples prepared by the above-described method were interposed between the positive electrode and the negative electrode, respectively, and wound up to assemble an electrode structure. As the cathode, an anode active material layer using graphite anode active material particles was formed on the copper thin film, and a cathode active material layer using lithium cobalt oxide was formed on the aluminum thin film as an anode. A nonaqueous electrolyte solution in which 1 mol of lithium hexafluorophosphate was dissolved in an organic solvent mixed with ethylene carbonate / ethylmethyl carbonate = 1/2 (volume ratio) was injected into the assembled electrode structure to prepare a lithium secondary battery.

C-rate characteristics of each lithium secondary battery manufactured by the above-described method were measured, and the results are shown in Table 1 below.

Referring to the results of Table 1, the discharge capacity of the battery employing the separator of Example 1 having a low resistance under the high rate discharge condition was higher than that of the comparative examples although it did not exhibit a large difference in the low rate discharge.

Claims (16)

(S1) preparing a porous substrate having pores;
(S2) coating the nonwoven fabric on at least one surface of the porous substrate;
(S3) coating a slurry on which the inorganic particles are dispersed and in which the binder polymer is dissolved in the solvent, on the coated non-solvent; And
(S4) The non-solvent and the solvent are simultaneously dried, and the inorganic particles are connected and fixed to each other by the binder polymer, so that the porous organic-inorganic composite layer containing pores formed by the interstitial volume between the inorganic particles To form on the porous substrate,
The steps (S2) and (S3)
Characterized in that the slurry is continuously coated on the coated non-solvent through the second slot while using a die having two adjacent slots and coating the non-solvent on one side of the porous substrate through the first slot , And a method for producing the separator. The method according to claim 1,
Wherein the porous substrate is a polyolefin-based porous film. The method according to claim 1,
Wherein the porous substrate has a thickness of 1 to 100 mu m. The method according to claim 1,
Wherein the binder polymer has a solubility index of 15 to 45 MPa &lt; ^{1/2 &} gt ;. The method according to claim 1,
The binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, 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, cyanoethylpyrrolidone, Polyvinyl alcohol (cyanoethylpolyviny a binder polymer selected from the group consisting of lanolin, lauroyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan and carboxyl methyl cellulose, or a mixture of two or more thereof And the mixture is a mixture. delete The method according to claim 1,
Wherein the difference in solubility index between the binder polymer and the solvent is 5.0 Mpa ^1/2 or less. The method according to claim 1,
Wherein the non-solvent is one of non-solvent selected from the group consisting of water, methanol, ethanol, ethylene glycol, and glycerol, or a mixture of two or more thereof. The method according to claim 1,
The solvent may be selected from the group consisting of acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, pyrrolidone, NMP) and cyclohexane, or a mixture of two or more of them. The method according to claim 1,
Wherein the boiling point of the non-solvent is at least the boiling point of the solvent. The method according to claim 1,
Wherein the average particle diameter of the inorganic particles is 0.001 to 10 占 퐉. The method according to claim 1,
Wherein the weight ratio of the inorganic particles to the binder polymer is 50:50 to 99: 1. The method according to claim 1,
Wherein the coating thickness of the non-solvent is 5 to 250 탆. delete delete delete

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