KR101751443B1 - Separator having porous coating layer and electrochemical device having the same - Google Patents

Abstract

The separator of the present invention comprises: a porous substrate having a plurality of pores; And a porous coating layer coated on at least one surface of the porous substrate and formed of a mixture of a plurality of inorganic particles and a binder polymer, wherein the binder polymer comprises a first binder having a weight average molecular weight of 100,000 to 1,000,000, And a second binder polymer having a weight average molecular weight of 100 to 10,000.
According to the present invention, the porous coating layer formed on the outer surface of the porous substrate is made of an inorganic material having excellent thermal stability, so that even when the electrochemical device is overheated, a short circuit between the anode and the cathode can be suppressed.
In addition, by using two kinds of polymer binders having different molecular weights, it is possible to maintain the porosity of the separator while improving the binding property of the separator to other base materials, thereby securing excellent battery performance and preventing the separation of inorganic particles in handling of the separator .

Description

TECHNICAL FIELD [0001] The present invention relates to a separator having a porous coating layer and an electrochemical device having the separator. [0002]

The present invention relates to a separator of an electrochemical device such as a lithium secondary battery, and to an electrochemical device having the separator. More particularly, the present invention relates to an organic / inorganic composite separator including a polymeric binder having a different molecular weight and an electrochemical device comprising the same. will be.

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-based porous substrate commonly used as a separator of an electrochemical device exhibits extreme heat shrinkage behavior at a temperature of 100 DEG C or higher owing to the characteristics of the manufacturing process including material properties and elongation, . ≪ / RTI >

In order to solve the safety problem of such an electrochemical device, a separator in which a porous coating layer is formed by coating a mixture of an excess of inorganic particles and a binder polymer on at least one surface of a porous substrate having a plurality of pores has been proposed. In the separator in which the porous coating layer is formed, the inorganic particles 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 suppressing heat shrinkage of the porous substrate upon heat- Thereby preventing both electrodes from short-circuiting during congestion. In addition, interstitial volumes exist between the inorganic particles to form micropores.

In order for the organic-inorganic composite porous coating layer formed on the porous substrate to excellently exhibit the above-described function, the inorganic particles must be contained in a predetermined amount or more. However, as the content of the inorganic particles increases, the content of the binder polymer becomes relatively small. Therefore, the binding property with the electrode decreases, and the stress generated in the process of assembling the electrochemical device, such as winding, Of the inorganic particles are liable to desorb. The desorbed inorganic particles act as local defects of the electrochemical device, adversely affecting the safety of the electrochemical device.

Therefore, there is a need for a separator having excellent adhesion and having improved performance for preventing the separation of inorganic particles.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a separator containing an organic-inorganic mixture having improved adhesion, and an electrochemical device having the same, in place of a separator having a porous coating layer containing a conventional organic-inorganic mixture .

In order to solve the above problems, the separator of the present invention comprises: a porous substrate having a plurality of pores; And a porous coating layer coated on at least one surface of the porous substrate and formed of a mixture of a plurality of inorganic particles and a binder polymer, wherein the binder polymer comprises a first binder having a weight average molecular weight of 100,000 to 1,000,000, And a second binder polymer having a weight average molecular weight of 100 to 10,000.

The content of the second binder polymer is preferably 1 to 60% by weight based on the content of the first binder polymer.

In the separator of the present invention, the first binder polymer may include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, Polyvinylpyrrolidone, polyvinylacetate, ethylene-vinyl acetate copolymer (polyethylene-co), polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylacetate, polyvinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl Cyanoethylpullulan, But are not limited to, ethylenevinyl alcohol, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-butadiene- Styrene copolymer and polyimide may be used.

In the separator of the present invention, the second binder polymer may be a rosin-based resin, a terpene-based resin, or a petroleum resin.

The rosin-based resin is preferably abietic acid, levopimaric acid or neoabietic acid.

Examples of the terpene resin include terpene resins such as alpha-pinene, beta-pinene, dipentene, alpha-pinene phenol resin, dipenthene phenol resin, dipentene phenol resin, or terpene phenol resin.

The petroleum resin is preferably an aliphatic (C5) petroleum resin, an aromatic (C9) petroleum resin, a copolymerized petroleum resin, a dicyclopentadiene (DCPD) resin or a hydrogenated resin.

In the separator of the present invention, it is preferable that the inorganic particles have an average particle diameter of 0.001 to 10 탆 and a dielectric constant of 5 or more, inorganic particles having a lithium ion transporting ability, and a mixture thereof.

The 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, 0 <x < _{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 , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ .

The 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 <3), lithium aluminum titanium phosphate _{Li x Al y Ti z (PO} 4) 3, 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) x O y series glass (0 <x <4, 0 <y < 4), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 0 < (Li _x N _y , 0 <x <4, 0 <y <2), SiS ₂ (Li _x Si _y S _z (0 <y <1, 0 <z < 0 <x <3, 0 <y <3, 0 <z <4) series glass and P ₂ S ₅ (Li _x P _y S _z , 7) series glass can be used.

In addition, it is preferable to use inorganic particles and binder polymer having a weight ratio of 50:50 to 99: 1.

In the separator of the present invention, the porous substrate may be a polyolefin-based porous substrate.

The polyolefin-based porous substrate is preferably polyethylene, polypropylene, polybutylene, and polypentene.

The thickness of the porous substrate is preferably 5 to 50 μm, and the pore size and the porosity are preferably 0.01 to 50 μm and 10 to 95%, respectively.

The separator of the present invention can be applied to a separator of an electrochemical device such as a lithium secondary battery or a supercapacitor.

According to the present invention, the porous coating layer formed on the outer surface of the porous substrate is made of an inorganic material having excellent thermal stability, so that even when the electrochemical device is overheated, a short circuit between the anode and the cathode can be suppressed.

In addition, by using two kinds of polymer binders having different molecular weights, it is possible to maintain the porosity of the separator while improving the binding property of the separator to other base materials, thereby securing excellent battery performance and preventing the separation of inorganic particles in handling of the separator .

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a SEM photograph of the surface of a separator in Examples and Comparative Examples 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.

In the separator according to the present invention,

A porous substrate having a plurality of pores; And an organic / inorganic composite separator coated on at least one surface of the porous substrate, the porous coating layer being formed of a mixture of a plurality of inorganic particles and a binder polymer,

The binder polymer includes a first binder polymer having a weight average molecular weight of 100,000 to 1,000,000 and a second binder polymer having a weight average molecular weight of 100 to 10,000.

The porous coating layer of the present invention is formed of a mixture of two kinds of first binder polymer and second binder polymer having different molecular weights from inorganic particles.

The inorganic particles serve as a kind of spacer capable of maintaining the physical shape of the porous coating layer, thereby suppressing heat shrinkage of the porous substrate when the electrochemical device is overheated, or preventing shorting of both electrodes when thermal runaway occurs. In addition, interstitial volumes exist between the inorganic particles to form micropores.

The binder polymer plays a role of fixing the inorganic particles and providing the adhesion with the other substrate. Since the second binder polymer having a relatively low molecular weight in the drying process of the coating layer is excellent in mobility, the first binder polymer is free to move compared with the first binder polymer bound to the inorganic particles, and is distributed at a high density on the surface of the coating layer. Due to the high density of the first binder polymer on the surface of the coating layer, the binding property with the electrode is improved and the separation of the inorganic particles can be prevented. Also, since the second binder polymer having excellent mobility has a high possibility of penetration of the porous substrate into the void, the binding strength between the coating layer and the porous substrate is also improved.

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 the first binder polymer having a weight average molecular weight of 100,000 to 1,000,000 include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride (trichlorethylene), polyvinylidene fluoride -co-trichlorethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate But are not limited to, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylfluoran ( cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile butadiene styrene (Acrylonitrile-butadiene-styrene) copolymer and polyimide.

Further, examples of the second binder polymer having a weight average molecular weight of 100 to 10000 include rosin-based resins, terpene-based resins, and petroleum resins.

The rosin-based resin is preferably abietic acid, levopimaric acid or neoabietic acid.

Examples of the terpene resin include terpene resins such as alpha-pinene, beta-pinene, dipentene, alpha-pinene phenol resin, dipenthene phenol resin, dipentene phenol resin, or terpene phenol resin.

The petroleum resin is preferably an aliphatic (C5) petroleum resin, an aromatic (C9) petroleum resin, a copolymerized petroleum resin, a dicyclopentadiene (DCPD) resin or a hydrogenated resin.

In the porous coating layer formed of a mixture of a plurality of inorganic particles and a binder polymer, 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. Nonlimiting 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, 0 < , 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, and the like _{CaO, ZnO, ZrO 2, SiO} 2, Y 2 O 3, Al 2 O 3, SiC , and TiO ₂ or mixtures 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 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.

As the porous substrate, any porous substrate such as a porous membrane or a nonwoven fabric formed of various polymers can be used as long as it is a planar porous substrate commonly used in an electrochemical device. For example, a polyolefin-based porous film used as an electrochemical device, particularly a separator of a lithium secondary battery, or a nonwoven fabric made of polyethylene terephthalate fiber may be used, and the material and shape thereof 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 0.01 to 50 占 퐉 and 10 To 95%.

According to the present invention, the porous coating layer formed on the outer surface of the porous substrate is made of an inorganic material having excellent thermal stability, so that even when the electrochemical device is overheated, a short circuit between the anode and the cathode can be suppressed.

In addition, by using two kinds of polymer binders having different molecular weights, it is possible to maintain the porosity of the separator while improving the binding property of the separator to other base materials, thereby securing excellent battery performance. It is possible to prevent the separation of the inorganic particles in handling of the separator.

In the method for producing a separator of the present invention,

By coating a slurry in which inorganic particles are dispersed and a binder polymer dissolved in a solvent on at least one surface of the porous substrate to form a porous coating layer.

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. 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.

As a method for coating the porous substrate with the slurry in which the inorganic particles are dispersed and the binder polymer is dissolved in the solvent, a conventional coating method known in the art may be used. For example, a dip coating, a die coating , Roll coating, comma coating, or a combination thereof. Further, the porous coating layer can be selectively formed on both or only one side of the porous substrate.

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

The electrochemical device of the present invention includes all devices that perform an electrochemical reaction, and specific examples thereof 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.

In the electrochemical device of the present invention, an electrolyte in which a salt having a structure such as A ⁺ B ^- is dissolved in an organic solvent can be selectively used. Wherein, A ⁺ is Li ^+, Na ^+, and comprising an alkali metal cation or an ion composed of a combination thereof, such as K ^+, B ^- is _{^{PF 6 -, BF 4 -,}} Cl -, Br -, I -, ClO Anions such as ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N (CF ₃ SO ₂ ) ₂ ^- and C (CF ₂ SO ₂ ) ₃ ^- do. Examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, (NMP), ethylmethyl carbonate (EMC), gamma-butyrolactone (g-butyrolactone), or mixtures thereof, but are not limited to, no.

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

Example 1. Preparation of separator with 1 wt% rosin resin

Al ₂ O ₃ 84.6% by weight of BaTiO _{3 and} 9.4% by weight of BaTiO ₃ was dissolved in acetone to prepare a slurry by adding 5% by weight of polyacrylonitrile as a binder polymer and 1% by weight of a rosin resin as a mixture of abietic acid and levopimaric acid . The slurry was coated on both sides of a 312HT film made by SK Corporation of polyolefin type and then dried to form a porous coating layer.

Example 2 Preparation of a Separator with 3% by Weight of Rosin Resin

Al ₂ O ₃ 82.8% by weight and BaTiO ₃ 9.2% by weight, 5% by weight of polyacrylonitrile as a binder polymer and 3% by weight of a rosin resin as a mixture of abietic acid and levopimaric acid were dissolved in acetone to prepare a slurry . The slurry was coated on both sides of a 312HT film made by SK Corporation of polyolefin type and then dried to form a porous coating layer.

Example 3 Preparation of a separator having 1 wt% of terpene resin

Al ₂ O ₃ 84.6% by weight of BaTiO _{3 and} 9.4% by weight of BaTiO ₃ and 5% by weight of polyacrylonitrile and 1% by weight of α-pinene phenol resin as a binder polymer were dissolved in acetone to prepare a slurry. The slurry was coated on both sides of a 312HT film made by SK Corporation of polyolefin type and then dried to form a porous coating layer.

Example  4. Petroleum resin  One % By weight Separator  Produce

Al ₂ O ₃ 84.6% by weight of BaTiO _{3 and} 9.4% by weight of BaTiO _3, and 5% by weight of polyacrylonitrile and 1% by weight of 1,6-cyclohexadiene with binder polymer were dissolved in acetone to prepare a slurry. The slurry was coated on both sides of a 312HT film made by SK Corporation of polyolefin type and then dried to form a porous coating layer.

Comparative Example 1. Preparation of a separator containing no second binder polymer

Al ₂ O ₃ 84.6% by weight of BaTiO _{3 and} 9.4% by weight of BaTiO ₃ and 6% by weight of polyacrylonitrile as a binder polymer were dissolved in acetone to prepare a slurry. The slurry was coated on both sides of a 312HT film made by SK Corporation of polyolefin type and then dried to form a porous coating layer.

Comparative Example 2. Preparation of a separator containing no second binder polymer

Al ₂ O ₃ 84.6% by weight of BaTiO _{3 and} 9.4% by weight of BaTiO ₃ and 6% by weight of polyacrylonitrile as a binder polymer were dissolved in acetone to prepare a slurry. The slurry was coated on both sides of a 312HT film made by SK Corporation of polyolefin type and then dried to form a porous coating layer.

Test Example 1. Measurement of Physical Properties of Separator

Measurement of Thickness

The thickness after pressing the separator produced in Example 1-4 and Comparative Example 1-2 with a force of 0.63 N using a TESA instrument was measured and is shown in Table 1 below.

Measurement of loading amount

The base film was cut to a size of 5 cm x 5 cm and then weighed. The separator was cut into 5 cm x 5 cm and weighed. The difference was divided by the unit area (1 m &lt; ² &gt; 4 and Comparative Example 1 were measured, and the results are shown in Table 1 below.

Measurement of Gurley Value

Separators were cut to a size of 5 cm x 5 cm and then passed through an amount of 50 ml of air using a Toyosiki Gurley type densometer. (Gurley) were measured and are shown in Table 1 below.

Measurement of Peel Strength

A separator cut at 15 mm × 50 mm was attached to the side of the 3M double-sided tape on the slide glass. The laminate was peeled at a rate of 300 mm / min using LLOYD LF-plus equipment after two laminations using a 1 kg weight roller The peel strengths of Examples 1-4 and Comparative Example 1 were measured and the results are shown in Table 1 below.

Thickness
(탆) Loading
(g / m ² ) Gurley
(sec / 50 ml) Peel Strength
(gf / 15 mm) Example 1
(rosin) 17.5 ± 0.1 15.1 ± 0.3 1,020 ± 250 44 ± 4 Example 2
(Rosin excess) 17.4 ± 0.2 15.0 ± 0.2 1,300 ± 120 93 ± 10 Example 3
(Terpene) 17.5 ± 0.2 15.4 ± 0.3 930 ± 30 48 ± 6 Example 4
(Petroleum resin) 17.3 ± 0.2 15.0 ± 0.3 810 ± 20 52 ± 5 Comparative Example 1 17.5 ± 0.2 15.8 ± 0.4 680 ± 30 16 ± 3 Comparative Example 2 17.4 ± 0.1 15.5 ± 0.2 850 ± 40 23 ± 3

According to the above Table 1, it can be seen that the adhesiveness with Gurley is superior to that of Comparative Example 1-2 in the case of Examples 1-4.

Test example 2. SEM measurement of the surface of the separator

SEM measurement of the surface of the separator produced in Example 1 and Comparative Example 1 is shown in Fig.

In the case of Example 1, a large amount of binder is distributed between the inorganic particles, and the adhesive force is measured to be high due to such a binder. On the other hand, in the case of Comparative Example 1, it can be seen that no binder was observed between the inorganic particles.

Claims (17)

A porous substrate having a plurality of pores; And an organic / inorganic composite separator coated on at least one surface of the porous substrate, the porous coating layer being formed of a mixture of a plurality of inorganic particles and a binder polymer,
The binder polymer is used for fixing inorganic particles and binding to an electrode and a porous substrate in an organic / inorganic composite separator. The binder polymer includes polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene But are not limited to, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, poly But are not limited to, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, , Cellulose acetate But are not limited to, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, A binder polymer selected from the group consisting of carboxyl methyl cellulose, acrylonitrile-butadiene-styrene copolymer and polyimide, or a mixture of two or more thereof, and has a weight average molecular weight A first binder polymer having a weight average molecular weight of 100,000 to 1,000,000 and a binder polymer selected from a rosin resin, a terpene resin and a petroleum resin, or a mixture of two or more thereof and a second binder polymer having a weight average molecular weight of 100 to 10,000 Organic / inorganic composite separator. The method according to claim 1,
Wherein the content of the second binder polymer is 1 to 60% by weight based on the content of the first binder polymer. delete delete The method according to claim 1,
Wherein the rosin-based resin is abietic acid, levopimaric acid, or neoabietic acid. The method according to claim 1,
The terpene resin may be selected from the group consisting of α-pinene, β-pinene, dipentene, α-pinene phenol resin, dipentene phenol resin, ) Or a terpene phenol resin. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The method according to claim 1,
Wherein the petroleum resin is an aliphatic (C5) petroleum resin, an aromatic (C9) petroleum resin, a copolymerized petroleum resin, a dicyclopentadiene (DCPD) resin or a hydrogenated resin. The method according to claim 1,
Inorganic composite separator characterized in that the inorganic particles have an average particle diameter of 0.001 to 10 탆. The method according to claim 1,
Wherein the inorganic particles are inorganic particles selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transporting ability, and mixtures thereof. 10. The method of claim 9,
The 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, 0 <x <_{<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, Wherein the inorganic particles are at least one inorganic particle selected from the group consisting of ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ , or a mixture of two or more thereof. 10. The method of claim 9,
The 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 <3), lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) _x O _y series glass <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , , 0 <y <1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 (Li x Si y S _{z, 0 <x <3,} 0 <y <2, 0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 <z &Lt; 7) series glass, or a mixture of two or more thereof. 10. The method of claim 9,
Inorganic composite separator wherein the weight ratio of the inorganic particles to the binder polymer is 50:50 to 99: 1. The method according to claim 1,
Inorganic composite separator, wherein the porous substrate is a polyolefin-based porous substrate. 14. The method of claim 13,
Wherein the polyolefin-based porous substrate is formed of any one selected from the group consisting of polyethylene, polypropylene, polybutylene, and polypentene. The method according to claim 1,
Inorganic composite separator, wherein the porous substrate has a thickness of 5 to 50 탆, a pore size and a porosity of 0.01 to 50 탆 and 10 to 95%, respectively. An electrochemical device comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
Wherein the separator is a separator according to any one of claims 1, 2 and 5 to 15. 17. The method of claim 16,
Wherein the electrochemical device is a lithium secondary battery.

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