KR20140060799A - Separator for electrochemical cell and method for making the same - Google Patents

Abstract

The present invention relates to a separator for an electrochemical device which is obtained by spraying and drying inorganic slurry to a temporary base material to obtain an inorganic slurry layer, thermal-melting the obtained inorganic slurry to a non-woven fabric, and removing the temporary base material from the inorganic slurry layer. A separator for an electrochemical device according to the present invention has excellent dimension stability, electrolyte wettability, easy controllable size of the pore of the separator, an easy controllable porosity, and a method for making the same. An electrochemical device manufactured by using the separator reduces battery resistance and improves performance.

Description

Separator for electrochemical device and method for manufacturing the same

More particularly, the present invention relates to a separation membrane for an electrochemical device obtained by thermally fusing a nonwoven fabric to one surface or both surfaces of an inorganic material layer, and a method for producing the same.

Recently, interest in energy storage technology is increasing. As cell phones, camcorders, notebook PCs, and even electric vehicles' energy are being expanded, efforts are being made to research and develop batteries. 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 ion secondary battery developed in the early 1990s has 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 It is becoming popular because of its advantage of being large.

Polyolefin-based resins are widely used as separator materials in lithium secondary batteries. Since the polyolefin-based separator has a property of melting at 200 ° C or less, the separator shrinks or melts at a high temperature, shorting both electrodes and / There is a problem that an explosion occurs.

Therefore, attempts have been made to use a nonwoven fabric that does not cause heat shrinkage at high temperatures as a separator material, but a large pore is formed in the separator made of a nonwoven fabric, thereby generating a leak current, . In addition, when the high-voltage lithium secondary battery is not fully charged due to the large pores of the nonwoven fabric or when the nonwoven fabric is coated with filler such as inorganic material, it is difficult to sufficiently fill the nonwoven fabric pores due to the use of the solvent and the size of the filler. And the tensile strength of the nonwoven fabric in the coating solvent is greatly decreased due to the characteristics of the nonwoven fabric substrate, which makes the workability of the process difficult.

Accordingly, a problem to be solved by the present invention is to provide a separator for an electrochemical device and a method for producing the same, which do not cause problems such as electric leakage without lowering the tensile strength of the nonwoven fabric when the nonwoven fabric is used as a separator material for electrochemical devices .

Another object of the present invention is to provide an electrochemical device having a separation membrane for an electrochemical device.

According to one aspect of the present invention, there is provided an organic electroluminescent device comprising: an inorganic layer; And a nonwoven fabric substrate fused to one or both surfaces of the inorganic material layer.

The nonwoven substrate may be made of polyolefin, polyester, polyamide, polyacetal, polycarbonate, polyimide, polyetheretherketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene microfiber, Lt; / RTI >

The inorganic layer may include inorganic particles and a binder polymer.

The binder polymer may be an aqueous binder polymer.

The inorganic particles may be one or a mixture of two or more selected from the group consisting of inorganic particles having a dielectric constant of 5 or more and inorganic particles having lithium ion transporting ability.

The nonwoven substrate may have a thickness between 5 um and 30 um and the inorganic layer may have a thickness between 5 um and 30 um.

According to another aspect of the present invention, there is provided a method for preparing a slurry, comprising: dispersing inorganic particles, a binder polymer, and other additives in a solvent to prepare an inorganic slurry; Coating the inorganic slurry on a temporary substrate and drying to obtain an inorganic layer on the temporary substrate; Thermally fusing the nonwoven fabric on the inorganic layer on the temporary substrate; And removing the temporary substrate from the inorganic layer.

The method may further include the step of thermally fusing the nonwoven fabric substrate to the surface of the inorganic layer so that the nonwoven fabric is formed on both surfaces of the inorganic layer after the temporary substrate is removed.

The thermal fusion may be performed at a temperature of 100 to 180 DEG C for 0.1 to 10 minutes under a pressure of 0.1 KPa to 1000 KPa.

The organic-inorganic hybrid membrane prepared according to the present invention has high dimensional stability even at a temperature of 200 ° C or higher and has excellent electrolyte wettability as compared with a polyolefin membrane. In addition, since the size and porosity of the separator are easily controlled by controlling the size of the inorganic particles, the separator / electrode is closely adhered to the separator through the hot pressing process And has a remarkable effect that the performance is improved. In addition, the selection of the nonwoven fabric material can be varied depending on the selection of the temperature of the thermal fusion process.

FIG. 1 is a photograph schematically showing a manufacturing process of a separation membrane according to the present invention.
2 is a photograph of a cross section of a separation membrane manufactured according to Example 1-1 of the present invention, taken by an electron microscope.
3 is a photograph of the surface of a separation membrane prepared according to Example 1-1 of the present invention, taken by an electron microscope.
4 is a cross-sectional photograph of a separation membrane produced according to Comparative Example 1-1 of the present invention.
5 is a graph showing a pore size distribution diagram of a separation membrane produced according to Example 1-1 and Comparative Example 1-1 of the present invention.
6 is a graph showing the charge and discharge of the lithium secondary battery produced in Example 1-2 and Comparative Example 1-2.
7 is a graph showing charge / discharge cycles of Example 1-2.

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 construed 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 separator of the present invention has a constitution in which a nonwoven fabric is fused to one or both surfaces of an inorganic material layer.

The kind of the inorganic substance is not particularly limited as long as it is electrochemically stable and does not cause oxidation and / or reduction reaction in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ). However, when inorganic particles having a high dielectric constant are used as an inorganic substance, dissociation of an electrolyte salt, for example, a lithium salt in the liquid electrolyte, can be enhanced and the ion conductivity of the electrolyte can be improved. Thus, the inorganic material has a dielectric constant of 5 or more, It is preferable to include high-permittivity inorganic particles having a particle diameter of 10 or more. Non-limiting examples of inorganic particles greater than a dielectric constant of 5 is _{BaTiO 3, Pb (Zr, Ti} ) O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB (Mg 3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), 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. In addition, 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 size of the inorganic particles is not limited, but it is preferable that the inorganic particles have a size in the range of 0.001 μm to 10 μm as much as possible in order to form a coating layer having a uniform thickness and a proper porosity. When the size of the inorganic particles is within the above range, the inorganic particles can be dispersed in a solvent to a certain level or more, the thickness of the inorganic layer within the desired range can be obtained, and an internal short circuit The probability of occurrence is lowered.

As the binder polymer to be used together with the inorganic particles, a binder polymer which is conventionally used for binding inorganic particles in the art can be used. Particularly, it is preferable to use a polymer having a glass transition temperature (T g) of -200 to 200 ° C because it can improve the mechanical properties such as the flexibility and elasticity of the finally formed inorganic layer . Such binder polymers connect and stably fix between inorganic particles or between inorganic particles and a nonwoven substrate.

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 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 solubility parameter of 15 to 45 MPa ^1/2 of a polymer, and the more preferred solubility parameter of 15 to 25 MPa ^1/2 and 30 to 45 MPa ^1/2 range. Therefore, it is preferable to use hydrophilic polymers having many polar groups, rather than hydrophobic polymers such as polyolefins.

Non-limiting examples of the binder polymer that can be used in the present invention include an aqueous binder polymer and a polyvinylidene binder polymer, and examples thereof include acrylonitrile-butadiene rubber, styrene-butadiene rubber, butadiene rubber (SBR), acrylic resin, hydroxyl ethyl cellulose and carboxyl methyl cellulose (CMC), polyvinylidene fluoride-hexafluoropropylene polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-trichlorethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, ), Polyvinylacetate, polyethylene-co-vinyl aceta (polyethylene-co-vinyl acetate) polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolulan, hydroxypropyl cellulose, hydroxypropyl cellulose, hydroxypropyl cellulose, A mixture of one or more kinds selected from the group consisting of cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose and pullulan can be mentioned.

The composition ratio of the inorganic particles and the binder polymer in the inorganic slurry for forming the inorganic material layer according to the present invention is 1 to 50 parts by weight or 5 to 30 parts by weight of the binder polymer based on 100 parts by weight of the inorganic material. When the composition ratio is within the above range, the pore size and porosity of the inorganic layer can be obtained within the desired range, and the inorganic particle binding can be appropriately performed.

The pore size and porosity of the inorganic layer are not particularly limited, but the pore size is preferably in the range of 0.001 μm to 10 μm, and the porosity is preferably in the range of 10 to 90%. The pore size and the porosity mainly depend on the size of the inorganic particles. For example, when inorganic particles having a particle size of 1 μm or less are used, pores formed are also about 1 μm or less. Such a pore structure is filled with an electrolyte solution to be injected at a later stage, and the filled electrolyte serves as an ion transfer function. When the pore size and porosity of the inorganic layer satisfy the above range, the inorganic layer does not act as a resistive layer and the mechanical properties of the inorganic layer can be prevented from lowering. The inorganic layer has a thickness of 5 [mu] m to 30 [mu] m.

In addition to the inorganic particles and the binder polymer described above as components constituting the inorganic layer in the separator of the present invention, other additives common in the art may be further included.

The inorganic layer may include inorganic particles, a binder polymer, and other additives conventionally used in the art.

The separator of the present invention uses a flat nonwoven fabric having a plurality of pores as a component.

The nonwoven fabric to be used in the present invention may be used without any particular limitation as long as it meets the intended purpose of the present invention. The thickness of the microfine fibers constituting the nonwoven fabric, the long diameter and porosity of the pores and the kind thereof are not particularly limited, Nonwoven fabrics can be exemplified.

The nonwoven fabric may be formed into a microfiber having an average thickness of 0.5 to 10 [mu] m or 1 to 7 [mu] m. When the average thickness of the microfine fibers constituting the nonwoven fabric satisfies the above range, the nonwoven fabric is easily produced, the desired mechanical properties are obtained, and the pore size of the nonwoven fabric can be easily controlled.

With respect to the size of pores (maximum diameter of pores) and pores formed in the nonwoven fabric, pores having a pore size of 0.1 μm to 70 μm may be contained in an amount of 50% or more based on the total number of pores. When the pore size and porosity are within the above range, not only the production of the nonwoven fabric is facilitated, but also the smooth movement of lithium ions can be ensured.

The nonwoven fabric may be made of a material selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as aramid, polyacetal, polycarbonate, polyimide, polyetheretherketone, Phenylene sulfide, polyethylene naphthalene, or the like, but is not limited thereto. Preferably, to improve the thermal stability of the nonwoven substrate, it is preferable to have a melting temperature of 200 ° C or higher.

It is preferred that the nonwoven substrate has a thickness between 5 um and 30 um.

The separation membrane formed by thermally welding the nonwoven fabric to the inorganic layer has a thickness thinner than the sum of the thicknesses of the inorganic layer and the nonwoven fabric.

A preferred method of producing the separator according to the present invention is illustrated below, but is not limited thereto (see FIG. 1).

Inorganic particles, binder polymer, and other additives are added to and dispersed in a solvent to prepare an inorganic slurry for producing an inorganic layer. Subsequently, the inorganic slurry is coated on the temporary substrate and dried to obtain the inorganic layer (1) on the temporary substrate (2). Subsequently, after the nonwoven fabric substrate 3 is thermally fused to the surface of the inorganic material layer 1 that is not in contact with the temporary substrate 2, the temporary substrate 2 formed on the inorganic material layer 1 is removed.

The solvent used in the inorganic slurry preferably has a solubility index similar to that of the binder polymer to be used and a low boiling point. This is to facilitate uniform mixing and subsequent solvent removal. Non-limiting examples of usable solvents include water, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, N-methyl-2-pyrrolidone (NMP), cyclohexane, or mixtures thereof.

After the inorganic particles are added to the binder polymer solution, the inorganic particles can be crushed. The disintegration time may be, for example, 1 to 20 hours, and the particle size of the disintegrated inorganic particles may be 0.001 to 10 um. As the crushing method, a conventional method can be used, and a ball mill method is particularly preferable.

In the specification of the present invention, the 'temporary substrate' is used as a substrate to which the inorganic slurry is applied in the process of producing the separator of the present invention, but the inorganic slurry is dried after the inorganic layer is formed and then removed after the non- Element.

The material of the temporary substrate is not particularly limited as long as it meets the requirements such as (P) transferability, heat resistance, workability, and low cost, but it preferably includes an antistick layer or release layer. Non-limiting examples of the temporary substrate types that can be used include a mixture of one or more selected from the group consisting of polyethylene terephthalate, polyester, polyamide, polycarbonate, fluoropolymer, polyacetal, polyolefin and polyimide .

The method of applying the inorganic slurry to the temporary substrate may be carried out by a conventional coating method known in the art under a constant humidity condition, for example, a humidity condition of 10 to 80%. For example, various methods such as doctor blade, dip coating, die coating, roll coating, comma coating, or a combination thereof can be used. As drying conditions, conventional drying conditions known in the art can be used, and for example, they can be dried at a temperature of 50 to 90 DEG C for 1 minute to 60 minutes. The dried inorganic layer has a thickness of from 5 μm to 30 μm.

The nonwoven fabric is thermally fused to the obtained inorganic material layer. The thermal fusion may be performed over the entire area in contact with the inorganic layer and the nonwoven fabric. The heat fusion is carried out at a temperature of 100 to 180 DEG C for 0.1 to 10 minutes at a pressure of 0.1 KPa to 1000 KPa.

According to an embodiment of the present invention, the nonwoven fabric base material may be thermally fused only to one side of the inorganic material layer, but two nonwoven fabric base materials may be thermally fused to both sides of the inorganic material layer, if necessary.

After the nonwoven fabric base material is thermally fused to one surface of the inorganic material layer, the temporary base material attached to the other surface of the inorganic material layer is removed. Then, if necessary, the nonwoven fabric substrate may be further thermally fused to the surface of the inorganic layer to which the temporary substrate has been attached.

The separation membrane manufactured as described above is interposed between the anode and the cathode and is manufactured from an electrochemical device.

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 cells, secondary cells, fuel cells, solar cells, and super capacitors . Particularly, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery is preferable.

The electrode to be applied together with the separator of the present invention is 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 A lithium complex oxide may be used. 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, Graphite or other carbon species may be used. Non-limiting examples of the positive electrode current collector include aluminum, nickel, or a foil produced by a combination of these. Non-limiting examples of the negative electrode current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil and so on.

Electrolyte that may be used in the present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, and B ^- is PF _{6 ^{-, BF 4 -, Cl -}} , Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO _{2) ^3-salt} containing an ion composed of the same anion, or a combination thereof, and a 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), ethylmethyl carbonate (EMC), gamma-butyrolactone, , 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.

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

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

Example  1-1: Preparation of Membrane

₂ parts by weight of sodium carboxymethyl cellulose (CMC) and 4 parts by weight of styrene-butadiene rubber (SBR) were dissolved in 100 parts by weight of alumina (Al ₂ O ₃ ) having an average particle diameter of 500 nm in water Mixed and ball milled to prepare an aqueous slurry having a solid content of 30% by weight. The prepared slurry was applied to a temporary polyethylene terephthalate (PET) film by a doctor blade method and dried in a 60 ° C drying oven for 60 minutes. The thickness of the alumina layer after drying was 10 μm. A polyethylene nonwoven fabric (Japan Vilene Company) having a thickness of 10 μm was faced to the dried alumina layer, heat-sealed at 120 ° C for 1 minute under 1 KPa pressure, and then the PET film was removed to obtain a composite film composed of an alumina / polyethylene nonwoven fabric Respectively. Then, a 10 μm-thick polyethylene nonwoven fabric was placed on the alumina surface from which the PET film had been removed, and then heat-sealed / pressed at 120 ° C. to obtain an organic-inorganic hybrid membrane according to the present invention. The thickness of the composite membrane was 25 μm, and the average pore size and porosity measured by a porosimeter were 0.43 μm and 55%, respectively. The average permeability of the obtained membrane was 330 sec / 100 ml in terms of Gurley number.

The cross-section and the surface of the obtained separation membrane are shown in FIGS. 2 and 3, respectively, and the average distribution of measured pores is shown in FIG.

Example  1-2: The lithium secondary battery  Produce

Cathode manufacturing

(PVDF) as a binder polymer, and carbon black as a conductive material in an amount of 96 wt%, 3 wt%, and 1 wt%, respectively, and a solvent N-methyl-2 Pyrrolidone (NMP) to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was applied to a copper (Cu) thin film as an anode current collector having a thickness of 10 .mu.m, followed by drying to prepare a negative electrode, followed by roll pressing.

Manufacture of anode

92% by weight of a lithium cobalt composite oxide as a positive electrode active material, 4% by weight of carbon black as a conductive material and 4% by weight of PVdF as a binder polymer were added to a solvent N-methyl-2-pyrrolidone (NMP) Slurry. The anode mixture slurry was applied to an aluminum (Al) thin film of a cathode current collector having a thickness of 20 μm and dried to produce a cathode, followed by roll pressing.

Manufacture of batteries

2032 coin cells were prepared with the above prepared positive electrode, negative electrode, separator, and electrolytic solution (ethylene carbonate (EC) / ethylmethyl carbonate (EMC) = 1/2 (volume ratio), lithium hexafluorophosphate (LiPF ₆ ) Respectively.

Comparative Example  1-1: Preparation of Membrane

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 . The alumina powder was added to the binder polymer solution so that the binder polymer / alumina weight ratio was 10/90 by weight, and the alumina powder was crushed and dispersed by a ball mill for about 12 hours to a particle size of about 500 nm to prepare a slurry Respectively. The slurry thus prepared was coated on a polyethylene terephthalate nonwoven fabric having a thickness of 10 mu m by a dip coating method. The coating was dried at 60 DEG C for 60 minutes to obtain a separator. The thickness of the resultant composite membrane was 26 [mu] m, and the average pore size and porosity measured by a porosimeter were 0.12 [mu] m and 68%, respectively. The average permeability of the obtained membrane was 1 sec / 100 ml as Gurley number.

A cross-sectional photograph of the obtained separation membrane is shown in FIG. 4, and an average distribution of pores is shown in FIG.

Comparative Example  1-2: The lithium secondary battery  Produce

A coin cell type lithium secondary battery was prepared in the same manner as in Example 1-2, except that the separator obtained in Comparative Example 1-1 was used.

Experimental Example : Of the battery Charging and discharging  Performance

The charging and discharging performance of the lithium secondary battery manufactured in Example 1-2 and Comparative Example 1-2 was tested twice, and the results are shown in FIGS. 6 and 7. FIG.

6 shows the first charge / discharge profile of the lithium secondary batteries of Examples 1-2 and Comparative Example 2 after activation (0.4 mA, constant current charge / discharge for 3 hours) of the lithium secondary battery. The lithium secondary battery of Example 1-2 was charged normally at a constant current (1 mA) - constant voltage (4.2 V, 0.5 mA current cut) in the range of 3 V to 4.2 V, whereas the lithium secondary battery of Comparative Example 1-2 The charging behavior was not observed at around 4.0 V at charging. This is because the pores of the separator of Comparative Example 1-2 are not appropriately controlled and a leakage current occurs at a high voltage.

7 is a charge / discharge cycle graph of the coin cell 2cell of Example 1-2. It can be seen that the capacity retention ratios of the lithium secondary batteries of Example 1-2 at 200 cycles of charging and discharging were as good as 89.5% and 90.3%, respectively.

As a result, it can be confirmed that the composite separator of the present invention is applicable as a secondary battery separator having excellent performance.

1: inorganic layer
2: Provisional equipment
3: Nonwoven fabric substrate

Claims (9)

Inorganic layer; And a nonwoven fabric substrate thermally fused to one or both surfaces of the inorganic material layer.
The method according to claim 1,
Wherein the nonwoven substrate is made of polyolefin, polyester, polyamide, polyacetal, polycarbonate, polyimide, polyetheretherketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene microfiber, Wherein the separator is formed of a material selected from the group consisting of tin, tin, and tin.
The method according to claim 1,
Wherein the inorganic layer comprises inorganic particles and a binder polymer.
The method of claim 3,
Wherein the inorganic particles are at least one selected from the group consisting of inorganic particles having a dielectric constant of 5 or more and inorganic particles having lithium ion transferring ability.
The method of claim 3,
Wherein the binder polymer is an aqueous binder polymer.
The method according to claim 1,
Wherein the nonwoven substrate has a thickness of 5 to 30 μm and the inorganic layer has a thickness of 5 to 30 μm.
Dispersing the inorganic particles, the binder polymer, and other additives in a solvent to prepare an inorganic slurry; Coating the inorganic slurry on a temporary substrate and drying to obtain an inorganic layer on the temporary substrate; Thermally fusing the nonwoven fabric on the inorganic layer on the temporary substrate; And removing the temporary substrate from the inorganic layer.
8. The method of claim 7,
Further comprising the step of thermally fusing the nonwoven fabric base material to the surface of the inorganic material layer so as to form a nonwoven fabric on both surfaces of the inorganic material layer after removing the temporary base material.
8. The method of claim 7,
Wherein the thermal fusion is performed at a temperature of 100 占 폚 to 180 占 폚 for 0.1 minute to 10 minutes under a pressure of 0.1 KPa to 1000 KPa.

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