KR101937320B1 - Separator for rechargeable battery and rechargeable battery including the same - Google Patents

Abstract

A porous base material, and a heat-resistant porous layer disposed on at least one surface of the porous base material and containing a fluorine-containing vinyl ether copolymer, and a lithium secondary battery comprising the separator.

Description

TECHNICAL FIELD [0001] The present invention relates to a separator for a secondary battery, and a lithium secondary battery including the separator. BACKGROUND ART [0002]

A separator for a secondary battery, and a lithium secondary battery including the separator.

 The separator for an electrochemical cell is an interlayer which keeps the ion conductivity while keeping the anode and the cathode isolated from each other in the battery, thereby enabling charging and discharging of the battery.

BACKGROUND ART [0002] In recent years, there has been a demand for a light-weight and miniaturization of a battery and a high-output large-capacity battery for use in an electric automobile. Accordingly, the separator may include a heat-resistant porous layer. In this case, the adhesion of the heat-resistant porous layer is important.

One embodiment provides a separator for a secondary battery in which adhesion of the heat resistant porous layer to a substrate and / or electrode is improved.

Another embodiment provides a secondary battery comprising the separator.

According to one embodiment, there is provided a separator for a secondary battery comprising a porous substrate and a heat resistant porous layer disposed on at least one side of the porous substrate and including a fluorine-containing vinyl ether copolymer.

According to another embodiment, there is provided a lithium secondary battery including a positive electrode, a negative electrode, and the separator positioned between the positive electrode and the negative electrode.

It is possible to improve the battery characteristics of the lithium secondary battery by providing the separator with improved adhesion to the substrate and / or the electrode.

FIG. 1 is a view showing a separator for a secondary battery according to one embodiment,
2 is an exploded perspective view of a lithium secondary battery according to an embodiment.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Hereinafter, a separator for a secondary battery according to one embodiment will be described.

FIG. 1 is a view showing a separator for a secondary battery according to one embodiment.

Referring to FIG. 1, a separator 10 for a secondary battery according to an embodiment includes a porous substrate 20 and a heat-resistant porous layer 30 disposed on one or both surfaces of the porous substrate 20.

The porous substrate 20 may have a plurality of pores and may be a porous substrate that can be used in an electrochemical device. Examples of the porous substrate 20 include, but are not limited to, polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetals, polyamides, polyimides, polycarbonates, polyetheretherketones, Polyetherimide, polyetherimide, polybenzimidazole, polyether sulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, tetrafluoroethylene (TEFLON) And polytetrafluoroethylene (PTFE), or a polymer membrane formed of a mixture of two or more thereof. Specifically, the porous substrate 20 may be a polyolefin-based substrate, and the polyolefin-based substrate is excellent in a shut down function and contributes to improvement of the safety of the battery. The polyolefin-based substrate may be selected from the group consisting of, for example, a polyethylene single film, a polypropylene single film, a polyethylene / polypropylene double film, a polypropylene / polyethylene / polypropylene triple film and a polyethylene / polypropylene / polyethylene triple film. Further, the polyolefin-based resin may include a non-olefin resin in addition to the olefin resin, or may include a copolymer of an olefin and a non-olefin monomer.

The porous substrate 20 may have a thickness of about 1 占 퐉 to 40 占 퐉 and may have a thickness of, for example, 1 占 퐉 to 30 占 퐉, 1 占 퐉 to 20 占 퐉, 5 占 퐉 to 15 占 퐉, and 5 占 퐉 to 10 占 퐉.

The heat resistant porous layer 30 includes a filler and a binder.

The filler may be, for example, an inorganic filler, an organic filler, an organic filler, or a combination thereof. The inorganic filler may be a ceramic material capable of improving heat resistance, and may include, for example, a metal oxide, a metalloid oxide, a metal fluoride, a metal hydroxide, or a combination thereof. The inorganic filler may be selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, GaO, ZnO, ZrO ₂ , Y ₂ O ₃ , _{SrTiO 3, BaTiO 3, Mg (} OH) 2 , or however a combination thereof, and the like. The organic filler may include, but is not limited to, an acrylic compound, an imide compound, an amide compound, or a combination thereof. The organic filler may have a core-shell structure, but is not limited thereto.

The filler may be spherical, plate or cubic with a size of about 1 nm to 2000 nm. For example, the filler may comprise a cubic filler. The filler may have a size of about 100 nm to 1000 nm, and may be within the range of about 100 nm to 800 nm. Here, the size may be an average particle size or a long diameter. By using a filler having a size within the above range, appropriate strength can be imparted to the heat resistant porous layer 30. The fillers may be used in a mixture of two or more different types or different sizes. By including the filler, the heat resistance is improved, and it is possible to further prevent the separator from being rapidly shrunk or deformed due to the temperature rise.

The binder functions to fix the filler on the porous substrate 20 and to adhere well to the porous substrate 20 on one side of the heat resistant porous layer 30 and adhere well to the electrode To provide an adhesive force.

The binder may include a fluorine-containing vinyl ether copolymer.

The fluorine-containing vinyl ether copolymer may contain, for example, fluoroethylene segments and alkyl vinyl ether segments, such as alternating copolymers in which a fluoroethylene moiety and an alkyl vinyl ether moiety are alternately distributed , Randomly distributed random copolymers, or graft copolymers grafted in part, but the present invention is not limited thereto.

The fluorine-containing vinyl ether copolymer may have a hydroxyl group.

The above-mentioned fluorine-containing vinyl ether copolymer has good air permeability and can improve the air permeability of the separator.

Further, the fluorine-containing vinyl ether copolymer has a relatively low glass transition temperature, so that it is possible to obtain a high adhesive property between the porous substrate 20 and the heat resistant porous layer 30 and / or between the heat resistant porous layer 30 and the electrode at the process temperature Can be provided. Accordingly, it is possible to reduce deformation of the separator at a high temperature and to prevent detachment between the porous substrate 20 and the heat resistant porous layer 30 and / or between the separator and the electrode, thereby improving battery characteristics.

The fluorine-containing vinyl ether copolymer may have a glass transition temperature of, for example, about 80 캜 or lower, and may have a glass transition temperature of, for example, about 65 캜 or lower within the above range, Can have a glass transition temperature. The fluorine-containing vinyl ether copolymer may have a glass transition temperature of, for example, about 25 ° C to 80 ° C, and may have a glass transition temperature of, for example, about 30 ° C to 65 ° C within the above range, Lt; RTI ID = 0.0 > 30 C < / RTI >

In addition, the fluorine-containing vinyl ether copolymer can be easily dispersed and / or dissolved in an aqueous solution by having a hydroxyl group, so that it can be effectively used in a water-based coating process and can be crosslinked with a polymer contained in an aqueous composition.

The fluorine-containing vinyl ether copolymer may be included in an amount of about 5 wt% to 100 wt% based on the total amount of the binder, and may be included in the range of about 10 wt% to 100 wt% 20% by weight to 100% by weight, and within the range of about 30% by weight to 100% by weight.

The binder may further comprise one or more than two kinds of binders in addition to the fluorine-containing vinyl ether copolymer described above.

The binder contains at least one of a vinyl group, a (meth) acrylate group, an epoxy group, an oxetane group, an ether group, a cyanate group, an isocyanate group, a hydroxyl group, a carboxyl group, a thiol group, an amino group, an alkoxy group, But it is not limited thereto.

The binder may be, for example, a vinylidene fluoride-based polymer such as polyvinylidene fluoride (PVdF) homopolymer or polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer, polymethyl methacrylate, Polyvinyl pyrrolidone, polyvinyl acetate, polyethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol But are not limited to, polyvinylpyrrolidone, cyanoethylcellulose, cyanoethylstarch, pullulan, carboxymethylcellulose, acrylonitrile-styrene-butadiene copolymers, or combinations thereof.

For example, the binder may further include an aqueous binder. The aqueous binder may further include at least one selected from, for example, acrylic latex, polyvinylidene fluoride (PVdF) latex and polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer latex, It is not.

In one example, the binder may further include a binder in the form of particles. The binder in particulate form may further comprise at least one selected from, for example, acrylic binder, polyvinylidene fluoride (PVdF) binder and polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer binder, It is not.

The heat-resistant porous layer 30 may have a thickness of about 0.01 μm to 20 μm, and may have a thickness of about 1 μm to 10 μm within the above range, and a thickness of about 1 μm to 5 μm Lt; / RTI >

The separator for a secondary battery can be formed, for example, by applying a composition for a heat resistant porous layer to one surface or both surfaces of a porous substrate 20 and drying the same.

The composition for the heat resistant porous layer may contain the above-mentioned binder, the above-described filler and a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the above-mentioned binder and the filler described above. The solvent may be, for example, water, acetone, methyl ethyl ketone, ethyl isobutyl ketone, tetrahydrofuran, dimethyl formaldehyde, cyclohexane or a mixture thereof, but is not limited thereto. The solvent may be water, for example.

The application may be, for example, spin coating, dip coating, bar coating, die coating, slit coating, roll coating, inkjet printing, and the like, but is not limited thereto.

The drying can be performed by, for example, a method of drying by natural drying, hot air, hot air or low-humidity wind, vacuum drying, far-infrared ray, electron beam, etc., but is not limited thereto. The drying process may be performed at a temperature of, for example, 25 ° C to 120 ° C, and may be performed at a temperature of, for example, about 80 ° C to 100 ° C for about 5 seconds to 60 seconds, .

The separator for a secondary battery may be manufactured by a method such as lamination, coextrusion or the like in addition to the above-described method.

The lithium secondary battery including the above-described separator for a secondary battery will be described below.

The lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to the type of the separator and the electrolyte used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

Here, a prismatic lithium secondary battery is exemplarily described as an example of a lithium secondary battery.

2 is an exploded perspective view of a lithium secondary battery according to an embodiment.

2, the lithium secondary battery 100 according to an embodiment includes an electrode assembly 60 and an electrode assembly 60 wound between the anode 40 and the cathode 50 with the separator 10 interposed therebetween. And includes a built-in case 70.

The electrode assembly 60 may be in the form of a jelly roll formed by winding the anode 40 and the cathode 50 with the separator 10 interposed therebetween.

The anode 40, the cathode 50 and the separator 10 are impregnated with an electrolyte (not shown).

The anode 40 may include a cathode current collector and a cathode active material layer formed on the cathode current collector. The cathode active material layer may include a cathode active material, a binder, and optionally a conductive material.

The cathode current collector may be aluminum (Al), nickel (Ni) or the like, but is not limited thereto.

As the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Concretely, at least one of cobalt, manganese, nickel, aluminum, iron or a composite oxide or composite phosphorus of a metal and lithium in combination thereof may be used. More specifically, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate or a combination thereof may be used.

The binder not only adheres the positive electrode active materials to each other well but also adheres the positive electrode active material to the positive electrode current collector. Specific examples thereof include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride , Carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like. These may be used alone or in combination of two or more.

The conductive material imparts conductivity to the electrode. Examples of the conductive material include, but are not limited to, natural graphite, artificial graphite, carbon black, carbon fiber, metal powder, and metal fiber. These may be used alone or in combination of two or more. The metal powder and the metal fiber may be made of metals such as copper, nickel, aluminum, and silver.

The cathode 50 may include a negative electrode collector and a negative electrode active material layer formed on the negative collector.

The negative electrode current collector may be copper (Cu), gold (Au), nickel (Ni), copper alloy, or the like, but is not limited thereto.

The negative electrode active material layer may include a negative electrode active material, a binder, and optionally a conductive material.

Examples of the negative electrode active material include a material capable of reversibly intercalating and deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, a transition metal oxide, Can be used.

Examples of the material capable of reversibly intercalating and deintercalating lithium ions include carbonaceous materials, and examples thereof include crystalline carbon, amorphous carbon, and combinations thereof. Examples of the crystalline carbon include amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke, and the like. As the lithium metal alloy, a lithium-metal alloy may be selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, An alloy of a selected metal may be used. As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-Y alloy, Sn, SnO ₂ , Sn-C composite, Sn- And at least one of them may be mixed with SiO ₂ . The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Se, Te, Po, and combinations thereof. Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The kind of the binder and the conductive material used for the cathode may be the same as the binder and the conductive material used in the anode.

The positive electrode 40 and the negative electrode 50 can be produced by mixing each of the active materials and the binder with a conductive material in a solvent to prepare each active material composition and applying the active material composition to each current collector. The solvent may be N-methyl pyrrolidone or the like, but is not limited thereto. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein.

The separator 10 is as described above.

The electrolytic solution includes an organic solvent and a lithium salt.

The organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specific examples thereof may be selected from a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent and an aprotic solvent.

As the organic solvent, for example, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethyl ethyl acetate, methyl propionate , Ethyl propionate,? -Butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. Examples of the non-protonic solvent include R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, A double bond aromatic ring or an ether bond); amines such as dimethylformamide; dioxolanes such as 1,3-dioxolane; sulfolanes; and the like.

The organic solvents may be used alone or in combination of two or more. When two or more of them are used in combination, the mixing ratio may be appropriately adjusted according to the performance of the desired cell.

The lithium salt is dissolved in an organic solvent to act as a source of lithium ions in the battery to enable operation of a basic lithium secondary battery and accelerate the movement of lithium ions between the positive electrode and the negative electrode. For example the lithium salt _{is, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiN (SO 3 C 2 F 5) 2, LiN (CF 3 SO 2) 2, LiC 4 F 9 SO 3, LiClO 4, LiAlO 2 , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) where x and y are natural numbers, LiCl, LiI, LiB (C ₂ O ₄ ) _2, But the present invention is not limited thereto.

The concentration of the lithium salt can be used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolytic solution has an appropriate conductivity and viscosity, and thus can exhibit excellent electrolytic solution performance, and lithium ions can effectively move.

The lithium secondary battery including the separator described above can be operated at a high voltage of 4.2 V or higher, and thus a high capacity lithium secondary battery can be realized without deteriorating the life characteristics.

Hereinafter, the aspects of the present invention described above will be described in more detail through examples. However, the following examples are for illustrative purposes only and do not limit the scope of the invention.

Separator  Produce

Example  One

3.3 g of acrylic latex (AX-4518, Zeon) and 6.6 g of a fluorine-containing vinyl ether copolymer (FE-4400, solid content 50% by weight, Asahi glass chemical) were added in succession to 83.5 g of demineralized water. And stirred for 1 hour. 6.6 g of boehmite (Boehmite, AOH60, manufactured by Navaltec) having an average particle size of 700 nm was added thereto, and the mixture was milled for 10 minutes using a bead mill to prepare a composition having a solid content of 10% by weight.

Subsequently, one surface of a polyethylene substrate (SK innovation Co., air permeability 140 sec / 100 cc) having a thickness of 9 μm was corona-treated, then the above composition was coated on a corona-treated surface and dried in an oven at 65 ° C. And then dried in an oven at 70 DEG C to prepare a separator for a secondary battery comprising a heat-resistant porous layer having a final thickness of 2 mu m.

Example  2

15 g of polyvinylidene fluoride latex (PVdF, RC10.246, Arkema), 3.3 g of acrylate latex (AX-4518, Zeon) and 0.1 g of fluorine-containing vinyl ether copolymer (FE-4400, ) Were successively added to 72.7 g of demineralized water and stirred at 25 DEG C for 1 hour using a stirrer to prepare a composition having a solid content of 10% by weight.

Subsequently, one surface of a polyethylene substrate (SK innovation Co., air permeability 140 sec / 100 cc) having a thickness of 9 μm was corona-treated, then the above composition was coated on a corona-treated surface and dried in an oven at 65 ° C. And then dried in an oven at 70 DEG C to prepare a separator for a secondary battery comprising a heat-resistant porous layer having a final thickness of 2 mu m.

Example  3

7.2 g of polyvinylidene fluoride latex (PVdF, RC10.246, Arkema), 3.3 g of acrylic latex (AX-4518, Zeon) and 4.3 g of fluorine-containing vinyl ether copolymer (FE-4400, Asahi glass chemical) Was added in turn to 80.5 g of demineralized water, and the mixture was stirred at 25 DEG C for 1 hour using a stirrer. To this was added 4.7 g of boehmite (Boehmite, AOH60, manufactured by Navaltec) having an average particle size of 700 nm and milled for 10 minutes using a bead mill to prepare a composition having a solid content of 10% by weight.

Subsequently, one surface of a polyethylene substrate (SK innovation Co., air permeability 140 sec / 100 cc) having a thickness of 9 μm was corona-treated, then the above composition was coated on a corona-treated surface and dried in an oven at 65 ° C. And then dried in an oven at 70 DEG C to prepare a separator for a secondary battery comprising a heat-resistant porous layer having a final thickness of 2 mu m.

Comparative Example  One

15 g of polyvinylidene fluoride latex (PVdF, RC10.246, Arkema), 3.3 g of acrylic latex (AX-4518, available from Zeon) and 0.5 g of vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP, RC 10.280, Arkema) were added in succession to 66.7 g of demineralized water and stirred at 25 DEG C for 1 hour using a stirrer to prepare a composition having a solid content of 10% by weight.

Subsequently, one surface of a polyethylene substrate (SK innovation Co., air permeability 140 sec / 100 cc) having a thickness of 9 μm was corona-treated, then the above composition was coated on a corona-treated surface and dried in an oven at 65 ° C. And then dried in an oven at 70 DEG C to prepare a separator for a secondary battery comprising a heat-resistant porous layer having a final thickness of 2 mu m.

Comparative Example  2

, 7.2 g of polyvinylidene fluoride latex (PVdF, RC10.246, Arkema), 3.3 g of acrylic latex (AX-4518, Zeon) and 0.5 g of vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP, RC 10.280 , Arkema) were added in succession to 77.7 g of demineralized water, and the mixture was stirred at 25 占 폚 for 1 hour using a stirrer. To this was added 4.7 g of boehmite (Boehmite, AOH60, manufactured by Navaltec) having an average particle size of 700 nm and milled for 10 minutes using a bead mill to prepare a composition having a solid content of 10% by weight.

Subsequently, one surface of a polyethylene substrate (SK innovation Co., air permeability 140 sec / 100 cc) having a thickness of 9 μm was corona-treated, then the above composition was coated on a corona-treated surface and dried in an oven at 65 ° C. And then dried in an oven at 70 DEG C to prepare a separator for a secondary battery comprising a heat-resistant porous layer having a final thickness of 2 mu m.

Comparative Example  3

30 g of polyvinylidene fluoride latex (PVdF, RC10.246, Arkema) and 3.3 g of acrylic latex (AX-4518, Zeon) were added in succession to 66.7 g of demineralized water and stirred at 25 DEG C for 1 hour using a stirrer A composition with a solids content of 10% by weight was prepared.

Subsequently, one surface of a polyethylene substrate (SK innovation Co., air permeability 140 sec / 100 cc) having a thickness of 9 μm was corona-treated, then the above composition was coated on a corona-treated surface and dried in an oven at 65 ° C. And then dried in an oven at 70 DEG C to prepare a separator for a secondary battery comprising a heat-resistant porous layer having a final thickness of 2 mu m.

Comparative Example  4

30 g of acrylic latex (BM900B, Zeon) and 3.3 g of acrylic latex (AX-4518, Zeon) were added in succession to 66.7 g of demineralized water and stirred at 25 DEG C for 1 hour using a stirrer to prepare a composition having a solid content of 10% Respectively.

Subsequently, one surface of a polyethylene substrate (SK innovation Co., air permeability 140 sec / 100 cc) having a thickness of 9 μm was corona-treated, then the above composition was coated on a corona-treated surface and dried in an oven at 65 ° C. And then dried in an oven at 70 DEG C to prepare a separator for a secondary battery comprising a heat-resistant porous layer having a final thickness of 2 mu m.

evaluation

A lithium secondary battery was produced by the following method.

LiCoO ₂ , polyvinylidene fluoride and carbon black were added to the N-methylpyrrolidone (NMP) solvent at a weight ratio of 96: 2: 2 to prepare a slurry. The slurry was coated on an aluminum (Al) foil having a thickness of 20 탆, dried and rolled to prepare a cathode having a thickness of 114 탆.

Natural graphite and artificial graphite were added to the N-methylpyrrolidone (NMP) solvent at a weight ratio of 1: 1 to prepare a slurry. The slurry was coated on a copper foil having a thickness of 20 탆, dried and rolled to prepare a negative electrode having a thickness of 130 탆.

Subsequently, the separator according to Examples 1 to 3 and Comparative Examples 1 to 4 was sandwiched between the positive electrode and the negative electrode and wound into a 7 cm * 6.5 cm jelly roll type electrode assembly.

An electrolyte solution in which 1.5 M of LiPF ₆ was added to a mixed solvent in which the electrode assembly was fixed to a case and ethylene carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) were mixed at a volume ratio of 2: 2: Was injected and sealed to produce a lithium secondary battery.

 (1) Dry adhesion

The electrode assembly was pressed twice at 90 캜 for 3 seconds under a pressure of 3 kgf / cm 2 to evaluate the dry adhesion. The dry adhesion strength is required in the production of a large-area separator. In Table 1, the larger the dry adhesion strength is, the stronger the adhesion and the smaller the dry adhesion strength is, the weaker the adhesion.

(2) Electrode adhesion

A charge and discharge cycle test was performed in which the lithium secondary battery was charged with a constant current until the voltage reached 4.2 V by a constant current constant voltage charging method at 60 캜 and then charged to a constant voltage and then discharged to 3.0 V with a constant current of 1C . The charge-discharge cycle test was carried out up to 500 cycles. The lithium secondary battery was then disassembled to evaluate the area ratio of the active material transferred to the surface of the separator. The larger the value of the electrode adhesive force, the stronger the adhesive property, and the smaller the dry adhesive force value, the weaker the adhesive property.

(3) The lithium secondary battery  life span

A lithium secondary battery was subjected to a charge-discharge cycle test in the same manner as in (2), and the capacity retention rate was evaluated. The higher the capacity retention rate, the smaller the capacity decrease during charging and discharging. The lower the capacity retention rate, the larger the capacity deterioration.

The results are shown in Table 1.

Dry adhesive force (Load gf) Electrode adhesion (%) Capacity retention rate (%) Example 1 1000 50 85 Example 2 3000 80 88 Example 3 2000 45 89 Comparative Example 1 800 40 83 Comparative Example 2 200 5 89 Comparative Example 3 <100 15 88 Comparative Example 4 4000 5 75

Referring to Table 1, it can be seen that the separator according to Examples 1 to 3 has improved dry adhesion and electrode adhesion as compared with the separator according to Comparative Examples 1 to 4. The lithium secondary batteries to which the separators according to Examples 1 to 3 were applied were confirmed to have equivalent or improved capacity retention rates after charge and discharge as compared with the lithium secondary batteries to which the separator according to Comparative Examples 1 to 4 was applied.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

10: Separator
20: Porous substrate
30: heat-resistant porous layer
40: anode
50: cathode
60: electrode assembly
70: Case

Claims (10)

Porous substrate, and
A heat-resistant porous layer disposed on at least one surface of the porous substrate and containing a fluorine-containing vinyl ether copolymer
/ RTI &gt;
The fluorine-containing vinyl ether copolymer includes fluoroethylene segments and alkyl vinyl ether segments,
The fluorine-containing vinyl ether copolymer has a glass transition temperature of 80 DEG C or lower
Separator for secondary battery.
delete The method of claim 1,
The fluorine-containing vinyl ether copolymer is a separator for a secondary battery having a hydroxyl group.
delete The method of claim 1,
Wherein the heat resistant porous layer further comprises an aqueous binder.
The method of claim 5,
Wherein the aqueous binder comprises at least one selected from an acrylic latex, a polyvinylidene fluoride (PVdF) latex, and a polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer latex.
The method of claim 1,
Wherein the heat resistant porous layer further comprises at least one selected from an acrylic binder, a polyvinylidene fluoride (PVdF) binder, and a polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer binder.
The method of claim 1,
Wherein the heat resistant porous layer further comprises a filler.
9. The method of claim 8,
Wherein the filler comprises a cubic filler.
anode,
Cathode, and
And a separator according to any one of claims 1, 3, and 5 to 9 located between the positive electrode and the negative electrode.

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