KR20120054883A - Preparation method of separator, separator formed therefrom, and electrochemical device having the same - Google Patents

Abstract

PURPOSE: A manufacturing method of a separator is provided to prevent the short circuit of both electrodes at overheating, to minimize pores-obstructing phenomenon by improving phenomenon binder polymer in slurry flows into pores of a porous substrate, thereby reducing the resistance increase of a separator due to the formation of porous organic-inorganic composite layer. CONSTITUTION: A manufacturing method of a separator comprises: a step of preparing porous substrate; a step of coating non-solvent(7) on at least one side of the porous substrate; a step of coating dispersed inorganic particles, slurry containing binder polymer dissolved in a solvent on a coated non-solvent; a step of drying the solvent and the non-solvent, connecting the inorganic particles each other by the binder polymer, thereby forming porous organic-inorganic composite layer on the porous substrate containing pores formed due to interstitial volume between the inorganic particles. The porous substrate is a polyolefin-based porous film.

Description

Method for manufacturing a separator, a separator formed therefrom, and an electrochemical device having the same {PREPARATION METHOD OF SEPARATOR, SEPARATOR FORMED THEREFROM, AND ELECTROCHEMICAL DEVICE HAVING THE SAME}

The present invention relates to a method for manufacturing a separator of an electrochemical device such as a lithium secondary battery, a separator formed therefrom, and an electrochemical device having the same, and more particularly, to a porous organic-inorganic composite including a mixture of inorganic particles and a binder polymer. The present invention relates to a method for manufacturing a separator coated with at least one surface of a porous substrate, a separator formed therefrom, and an electrochemical device having the same.

Recently, interest in energy storage technology is increasing. As the field of application extends to the energy of mobile phones, camcorders, notebook PCs, and even electric vehicles, efforts for research and development of electrochemical devices are becoming more concrete. The electrochemical device is the most attracting field in this respect, and the development of a secondary battery capable of charging and discharging has been the focus of attention, and in recent years in the development of such a battery in order to improve the capacity density and specific energy The research and development of the design of the battery is progressing.

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 has been considered as one of the next generation batteries by improving the weakness of the lithium ion battery, but the capacity of the battery is still relatively lower than that of the lithium ion battery, and the discharge capacity is improved due to insufficient discharge capacity at low temperatures. This is urgently needed.

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 an electrochemical device should not cause injury to the user in case of malfunction. For this purpose, safety standards strictly regulate the ignition and smoke in the electrochemical device. In the safety characteristics of the electrochemical device, there is a high possibility that an explosion occurs when the electrochemical device is overheated to cause thermal runaway or the separator penetrates. In particular, polyolefin-based porous membranes commonly used as separators for electrochemical devices exhibit extreme heat shrinkage behavior at temperatures of 100 degrees or more due to material properties and manufacturing process characteristics including elongation. There is a problem that causes.

In order to solve the safety problem of the electrochemical device, a separator having a porous organic-inorganic composite coating layer 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 has been proposed. For example, Korean Patent Publication No. 2007-0019958 discloses a porous organic-inorganic composite coating layer by coating and drying a slurry in which inorganic particles are dispersed on a porous substrate and a binder polymer dissolved in a solvent on a porous substrate such as a polyolefin membrane. A manufacturing method relating to a separator provided on a porous substrate is disclosed.

In the separator with the organic-inorganic composite porous coating layer, the inorganic particles present in the porous coating layer formed on the porous substrate serves as a kind of spacer to maintain the physical form of the porous coating layer, so that the porous substrate is heated when the electrochemical device is overheated. This prevents shrinkage or prevents short circuiting of both electrodes during thermal runaway. In addition, an interstitial volume exists between the inorganic particles to form fine pores.

As such, the organic-inorganic composite porous coating layer contributes to the thermal stability of the separator, but when forming the organic-inorganic composite porous coating layer, the binder polymer is introduced into the pores of the porous substrate to block some of the pores, thereby increasing the resistance of the separator. There is this.

Accordingly, the problem to be solved by the present invention is to solve the above-mentioned problems, the method of manufacturing a separator that can minimize the phenomenon that the pores of the porous substrate is blocked by the binder polymer when forming the organic-inorganic composite porous coating layer, the separator formed therefrom And to provide an electrochemical device having the same.

In order to achieve the above object, the separator manufacturing method of the present invention,

(S1) preparing a porous substrate having pores;

(S2) coating a non-solvent on at least one surface of the porous substrate;

(S3) coating a slurry having inorganic particles dispersed therein and a binder polymer dissolved in a solvent on the coated non-solvent; And

(S4) drying the non-solvent and the solvent at the same time so that the inorganic particles are connected and fixed to each other by a binder polymer, and the porous organic-inorganic composite layer including pores formed due to the interstitial volume between the inorganic particles. Allowing the porous substrate to be formed on the substrate.

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

In the separator production method of the present invention, the solubility index of the binder polymer is preferably 15 to 45 Mpa ^1/2 . Such binder polymers include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, and polymethylmethacrylate. , Polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer, polyethylene oxide ( polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyano Ethyl polyvinyl alcohol (cyanoethylpo) Lyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, etc. may be used alone or in combination of two or more of them. have.

In the separator manufacturing method of this invention, it is preferable that the difference in the solubility index of the said binder polymer and a nonsolvent is 5.5 Mpa ^1/2 or more, and the difference in the solubility index of the said binder polymer and a solvent is 5.0 Mpa ^1/2 or less. Non-solvents include water, methanol, ethanol, ethylene glycol, glycerol And the like may be used alone or in combination of two or more thereof, and as a solvent, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, etc. ), N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone (NMP), cyclohexane) and the like can be used alone or two or more of them 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 ㎛, and the weight ratio of the inorganic particles and the binder polymer is preferably 50:50 to 99: 1.

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

The separator of the present invention prepared by the above method may be interposed between the positive electrode and the negative electrode to manufacture an electrochemical device such as a lithium secondary battery or a super capacitor device.

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

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

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, thereby minimizing the clogging of the pores of the porous substrate. Accordingly, the increase in resistance of the separator due to the porous organic-inorganic composite layer is reduced.

1 is a process diagram schematically showing a method of manufacturing a separator according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the configurations described in the embodiments described herein are only one of the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, and various equivalents may be substituted for them at the time of the present application. It should be understood that there may be variations.

Hereinafter, the method for producing a separator according to the present invention will be described in detail.

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

As the porous substrate, any porous substrate commonly used in electrochemical devices such as a porous membrane or a nonwoven fabric formed of various polymers may be used. For example, a polyolefin-based porous membrane or a nonwoven fabric made of polyethylene terephthalate fiber, which is used as an electrochemical device, in particular, a separator of a lithium secondary battery, may be used. For example, the polyolefin-based porous membrane (membrane) is a polyolefin-based polymer such as polyethylene, polypropylene, polybutylene, polypentene, such as high density polyethylene, linear low density polyethylene, low density polyethylene, ultra high molecular weight polyethylene, or a mixture thereof. The polymer may be formed, and the nonwoven fabric may also be made of a fiber using a polyolefin-based polymer or a polymer having higher heat resistance. The thickness of the porous substrate is not particularly limited, but is preferably 1 to 100 μm, more preferably 5 to 50 μm, and the pore size and pore present in the porous substrate are also not particularly limited, but are 0.001 to 50 μm and 10, respectively. It is preferably from 95%.

Subsequently, a non-solvent is coated on at least one surface of the porous substrate (step S2).

In the present invention, non-solvent means a non-solvent for the binder polymer described later. As the non-solvent for the binder polymer, it is preferable to use ^one having a solubility index difference of 5.5 Mpa ^1/2 or more with the binder polymer. As a non-solvent, water, methanol, ethanol, ethylene glycol, glycerol, etc. can be used individually or in combination of 2 or more of these, respectively.

The coating thickness of the non-solvent is preferably 5 to 250 μm in consideration of the effect of the non-solvent coating and the efficiency according to the drying rate.

Then, the inorganic particles are dispersed and the binder polymer is dissolved in a 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 that can be used in the present invention are not particularly limited as long as the oxidation and / or reduction reactions do not occur in the operating voltage range (for example, 0 to 5 V on the basis of Li / Li ⁺ ) of the applied electrochemical device. In particular, when inorganic particles having a high dielectric constant are used as the inorganic particles, the ionic conductivity of the electrolyte may be improved by contributing to an increase in the dissociation degree of the electrolyte salt, such as lithium salt, in the liquid electrolyte.

For the reasons described above, the inorganic particles preferably include high dielectric constant 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, where 0 <x <1, 0 <y <1), Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), Hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO , NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO _2, SiC Or mixtures thereof.

In addition, the inorganic particles may be inorganic particles having lithium ion transfer capability, that is, inorganic particles containing lithium elements but having a function of transferring lithium ions without storing lithium. Non-limiting examples of inorganic particles having a lithium ion transfer capacity include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), Lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ (LiAlTiP) _x O _y series glass such as O ₅ (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3) , Li germanium thiophosphate such as Li _3.25 Ge _0.25 P _0.75 S ₄ (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5 ), Lithium nitride such as Li ₃ N (Li _x N _y , 0 <x <4, 0 <y <2), SiS ₂ based glass such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ (Li _x Si P ₂ S ₅ series glass (Li _x P _y S _z , 0 <x, such as _y S _z , 0 <x <3, 0 <y <2, 0 <z <4), LiI-Li ₂ SP ₂ S _5, etc. <3, 0 <y <3, 0 <z <7) or mixtures thereof.

In addition, the average particle diameter of the inorganic particles is not particularly limited, but for forming a coating layer of uniform thickness and proper porosity, it is preferably in the range of 0.001 to 10 μm. When the thickness is less than 0.001 μm, the dispersibility may be decreased, and when the thickness is more than 10 μm, the thickness of the coating layer formed may be increased.

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

In addition, the binder polymer does not necessarily have an ion conducting ability, but when a polymer having an ion conducting ability is used, the performance of the electrochemical device may be further improved. Therefore, the binder polymer is preferably as high as possible dielectric constant. In fact, since the dissociation degree of the salt in the electrolyte depends on the dielectric constant of the solvent of the electrolyte, the higher the dielectric constant of the binder polymer, the higher the dissociation of the salt in the electrolyte. The dielectric constant of the binder polymer may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), particularly preferably 10 or more.

In addition to the above-described function, the binder polymer may have a feature that can exhibit a high degree of swelling of the electrolyte by gelling upon impregnation of the liquid electrolyte. Accordingly, it is preferred to use polymers having a solubility index of 15 to 45 MPa ^1/2 , more preferred solubility indices in the range of 15 to 25 MPa ^1/2 and 30 to 45 MPa ^1/2 . Therefore, it is preferable to use hydrophilic polymers having more polar groups than hydrophobic polymers such as polyolefins. This is because when the solubility index is less than 15 MPa ^{1/2 and more} than 45 MPa ^1/2 , it is difficult to be swelled by a conventional battery liquid electrolyte.

Non-limiting examples of such binder polymers include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacryl Polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer (polyethylene-co-vinyl acetate) , Polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan ), Cyanoethylpolybi Cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, and the like, each of which may be used alone or among them. Two or more kinds can be mixed and used.

The weight ratio of the inorganic particles and the binder polymer is preferably in the range of 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 pore size and porosity of the coating layer formed by increasing the content of the polymer may be reduced. When the content of the inorganic particles exceeds 99 parts by weight, since the binder polymer content is small, the peeling resistance of the coating layer formed may be weakened.

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

Non-limiting examples of solvents that can be used 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, in consideration of ease of slurry coating and gelling of the binder polymer in the slurry, the solubility index difference between the binder polymer and the solvent is preferably 5 Mpa ^1/2 or less.

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

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 μm in consideration of the resistance and resistance of improving the stability of the battery.

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

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

Finally, the solvent in the slurry and the non-solvent coated on the porous substrate are simultaneously dried to remove 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. To include a porous organic-inorganic composite layer is formed on the porous substrate (step S4).

Referring to the properties of the porous organic-inorganic composite layer formed according to the production method of the present invention are as follows.

(S3) The result is a structure in which a non-solvent is coated on a porous substrate, and a slurry is coated thereon. The non-solvent layer serves as a kind of barrier layer that minimizes contact of the binder polymer dissolved in the slurry with the porous substrate. In addition, some of the binder polymer diffused into the non-solvent layer is estimated to gel or precipitate by the non-solvent to be difficult to enter the pores of the porous substrate.

(S3) When the resultant is passed through the dryer, the slurry coated on the non-solvent first receives heat or hot air. Thus, the solvent in the slurry coated on the outer portion dries at a faster rate than the nonsolvent. Accordingly, before the non-solvent coating layer is completely dried, pores are formed due to the interstitial volume between the inorganic particles while being connected and fixed to each other by the inorganic particles from the inorganic particles present at the outermost portion of the slurry coating layer. . In other words, due to the coating non-solvent layer, the binder polymer in the slurry is minimized to diffuse into the pores of the porous substrate during drying. This minimizes the clogging of the pores of the porous substrate by the binder polymer in the slurry, thereby improving the problem that the resistance of the separator due to the porous organic-inorganic composite layer is increased.

The porous organic-inorganic composite layer formed on the porous substrate through the above-described process is attached to each other (ie, the binder polymer is connected and fixed between the inorganic particles) so that the binder polymer can maintain the inorganic particles bound to each other. In addition, the porous organic-inorganic composite layer remains bound to the porous substrate by the binder polymer. The inorganic particles of the porous organic-inorganic composite layer are in close contact with each other, and the inorganic particles are in close contact with each other, and the interstitial volume generated when the inorganic particles are in contact with each other becomes the pores of the porous organic-inorganic composite layer.

The separator manufactured according to the above-described method may be manufactured, for example, by winding or laminating between an anode and a cathode to produce an electrochemical device. Electrochemical devices include all devices that undergo an electrochemical reaction, and specific examples include capacitors such as all kinds of primary, secondary cells, fuel cells, solar cells, or supercapacitor elements. 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 applied together with the separator of the present invention is not particularly limited, and according to a conventional method known in the art can be prepared in the form of an electrode active material bound to the electrode current collector. Non-limiting examples of the positive electrode active material of the electrode active material may be a conventional positive electrode active material that can be used for the positive electrode of the conventional electrochemical device, in particular lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide or combinations thereof It is preferable to use one lithium composite oxide. Non-limiting examples of the negative electrode active material may be a conventional negative electrode active material that can be used for the negative electrode of the conventional electrochemical device, in particular lithium metal or lithium alloys, carbon, petroleum coke, activated carbon, Lithium adsorbents such as graphite or other carbons are preferred. Non-limiting examples of the positive electrode current collector is a foil made by aluminum, nickel or a combination thereof, and non-limiting examples of the negative electrode current collector by copper, gold, nickel or copper alloy or a combination thereof Foils produced.

Electrolyte that may be used in the electrochemical device of the present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ comprises a Li ^+, Na ^+, an alkali metal cation or an ion composed of a combination thereof, such as K ⁺ B ^- 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 Salts containing ions consisting of anions such as (CF ₂ SO ₂ ) ₃ ^- or a combination thereof are propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl Carbonate (DPC), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate (EMC), gamma-butyrolactone or Some are dissolved or dissociated in an organic solvent composed of a mixture thereof, but are not limited thereto.

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

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example 1

PVdF-CTFE (polyvinylidene fluoride-chlorotrifluoroethylene copolymer) and Cyanoethylpullulan (cyanoethyl pullulan) were added to acetone in a weight ratio of 10: 2, respectively, and dissolved at 50 ° C. for at least 12 hours. Was prepared. Inorganic particles in which Al ₂ O ₃ powder and BaTiO ₃ powder were mixed in a weight ratio of 9: 1 were added to the polymer solution prepared so that the polymer / inorganic particles = 10/90 weight ratio, and the ball mill method was used for 12 hours or more. The slurry was prepared by crushing and dispersing the inorganic particles. The particle diameter of the inorganic particles of the slurry thus prepared was 600 nm on average.

Separately prepared methanol and the prepared slurry were continuously coated on one surface of a 12 μm thick polyethylene porous membrane (porosity 45%) through the slot die shown in FIG. 1. The coating thickness of methanol was 10 μm, and the coating amount of the slurry was 60 μm so that the thickness of the finally formed porous organic-inorganic composite layer was 4 μm.

The coated substrate was then passed through a drier controlled at a temperature of 50 degrees to dry the nonsolvent and the solvent to complete the separator.

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

Comparative Example 1

The separator was completed in the same manner as in Example 1, except that only the slurry was coated through the slot die shown in FIG. 1 without coating methanol. The coating amount of the slurry was adjusted so that the thickness of the finally formed porous organic-inorganic composite layer was 4 μm.

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

Comparative Example 2

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

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

The separators of the examples and the comparative examples manufactured by the above-described method were interposed between the positive electrode and the negative electrode, respectively, and then wound to assemble an electrode structure. As a negative electrode, a negative electrode active material layer using graphite negative electrode active material particles was formed on a copper thin film, and a positive electrode active material layer using lithium cobalt oxide was formed on an aluminum thin film. A non-aqueous electrolyte in which 1 mol of lithium hexafluorophosphate was dissolved in an organic solvent mixed with ethylene carbonate / ethyl methyl carbonate = 1/2 (volume ratio) was injected into the assembled electrode structure to prepare a lithium secondary battery.

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

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

Claims (16)

(S1) preparing a porous substrate having pores;
(S2) coating a non-solvent on at least one surface of the porous substrate;
(S3) coating a slurry having inorganic particles dispersed therein and a binder polymer dissolved in a solvent on the coated non-solvent; And
(S4) drying the non-solvent and the solvent at the same time so that the inorganic particles are connected and fixed to each other by a binder polymer, and the porous organic-inorganic composite layer including pores formed due to the interstitial volume between the inorganic particles. Method for producing a separator comprising the step of forming on the porous substrate. The method of claim 1,
The porous substrate is a method for producing a separator, characterized in that the polyolefin-based porous membrane. The method of claim 1,
The thickness of the porous substrate is a method for producing a separator, characterized in that 1 to 100 ㎛. The method of claim 1,
Method for producing a separator, characterized in that the solubility index of the binder polymer is 15 to 45 Mpa ^1/2 . The method of claim 1,
The binder polymer may be polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, Polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer, polyethylene oxide oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl Polyvinyl alcohol (cyanoethylpolyviny) lalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, any one binder polymer selected from the group consisting of two or more thereof A method for producing a separator, characterized in that the mixture. The method of claim 1,
The solubility index difference between the binder polymer and the non-solvent is 5.5 Mpa ^1/2 or more method for producing a separator. The method of claim 1,
The solubility index difference between the binder polymer and the solvent is 5.0 Mpa ^1/2 or less method for producing a separator. The method of claim 1,
The non-solvent is a 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 of claim 1,
The solvent is acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (N-methyl-2- A method for producing a separator, characterized in that any one selected from the group consisting of pyrrolidone, NMP) and cyclohexane or a mixture of two or more thereof. The method of claim 1,
The boiling point of the non-solvent is a method for producing a separator, characterized in that more than the boiling point of the solvent. The method of claim 1,
The average particle diameter of the inorganic particles is a method for producing a separator, characterized in that 0.001 to 10 ㎛. The method of claim 1,
Method for producing a separator, characterized in that the weight ratio of the inorganic particles and the binder polymer is 50:50 to 99: 1. The method of claim 1,
The coating thickness of the non-solvent is a method for producing a separator, characterized in that 5 to 250 ㎛. The separator formed according to the manufacturing method of the separator of any one of Claims 1-13. anode;
cathode; And
An electrochemical device interposed between the positive electrode and the negative electrode and having a separator formed according to the method of manufacturing a separator according to any one of claims 1 to 13. 16. The method of claim 15,
The electrochemical device is an electrochemical device, characterized in that the lithium secondary battery.

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