KR101915327B1 - A non-woven separator for a secondary battery - Google Patents

Abstract

The present invention relates to a nonwoven fabric separator for a secondary battery capable of producing a high output cell having uniform pore size and distribution with excellent resistance characteristics. In the nonwoven fabric separator according to the present invention, the microfine filaments and the microfine filaments are mixed, so that the pores are uniformly distributed in the nonwoven fabric and the pore diameter is uniformly formed. Therefore, the battery using the same as the separator has excellent resistance characteristics and high output characteristics, and current leakage is prevented even in the case of high current instantaneous discharge (10 seconds).

Description

[0001] The present invention relates to a separator for a secondary battery,

The present invention relates to a separation membrane for a secondary battery. More particularly, the present invention relates to a nonwoven fabric separator for a secondary battery, which is capable of producing a high-output cell having excellent resistance characteristics due to the uniformity of the pore size and distribution of the nonwoven fabric.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, laptops and even electric vehicles are expanded, efforts for research and development of electrochemical devices are becoming more and more specified. The electrochemical device is one of the most remarkable fields in this respect, and the development of a rechargeable secondary battery has become a focus of attention.

Among the currently applied secondary batteries, the lithium secondary batteries developed in the early 1990's are attracting attention because they have higher operating voltage and higher energy density than conventional batteries such as Ni-MH.

The lithium secondary battery is composed of an anode, a cathode, an electrolyte, and a separator. Among them, separator is required to separate and electrically isolate an anode and a cathode, and has high permeability (permeability) of lithium ion based on high porosity. To increase the ionic conductivity. Polyolefin-based materials, such as polyethylene (PE) and polypropylene (PP), which are advantageous for pore formation and have excellent chemical resistance, mechanical properties, and thermal properties, are mainly used as polymer substrates of separators used in general. Desirable characteristics include excellent air permeability, low heat shrinkage, and high piercing strength. However, due to the development of a high capacity and high output cell, continuous air permeability is required.

Due to the nature of the fiber structure, the nonwoven fabric exhibits a large nonuniformity in pore structure and size compared with the commercialized polyolefin separator, which is deteriorated in battery performance. Especially, it exhibits insufficient performance such as current leakage at a momentary high current momentary discharge (10 seconds). Therefore, it is required to develop a new nonwoven fabric separator which overcomes such shortcomings in the field of nonwoven fabric separator.

Accordingly, the present invention provides a separator for a secondary battery and a method of manufacturing the same, which can prevent the problems due to limitations and disadvantages of the related art.

The present invention relates to a novel separation membrane for solving the above problems. The separation membrane includes a novel nonwoven fabric substrate and an organic / inorganic composite porous coating layer formed on at least one side of the nonwoven fabric substrate. Wherein the nonwoven fabric substrate comprises a first filament yarn and a second filament yarn mixed in different diameters and the average diameter of the second filament yarn is 2 to 100 times the average diameter of the first filament yarn.

The nonwoven fabric substrate includes the first filament yarn and the second filament yarn in a ratio of 20:80 to 50:50 wt%.

The first filament yarn has a diameter of 200 nm to 1000 nm.

In the nonwoven fabric substrate, 80% or more of the pores formed in the nonwoven fabric substrate have a pore size of 0.1 to 0.5 탆.

The nonwoven fabric substrate has a thickness of 10 mu m to 35 mu m.

In addition, in the nonwoven fabric separator, the first filament yarn and the second filament yarn include a polyolefin-based polymer resin.

The organic / inorganic composite porous coating layer is formed on at least one surface of the nonwoven substrate and includes inorganic particles and a polymer resin.

The present invention also provides a secondary battery including the separator according to the present invention.

Since the separation membrane according to the present invention includes a nonwoven fabric substrate in which microfine filaments and microfine filaments are mixed, the pores are uniformly distributed in the nonwoven fabric and the pore diameter is uniformly formed. Therefore, the battery using the same as the separator has excellent resistance characteristics and high output characteristics, and current leakage is prevented even in the case of high current instantaneous discharge (10 seconds).

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
FIG. 1 shows a distribution of pore sizes of the separator according to Examples and Comparative Examples.
2 is a graph showing output characteristics of the separator according to the embodiment and the comparative example.
3 is a SEM photograph of a nonwoven fabric substrate according to an embodiment of the present invention.
4 is a SEM photograph of a nonwoven fabric substrate according to a comparative example of the present invention.

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 may designate the concept of a term appropriately in order to describe its own invention in the best way possible. It should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

The secondary battery separator contains an electrolyte and allows ion conduction between the anode and the cathode. The thickness and the pore distribution should be uniform. For example, if the thickness of a specific portion of the separator is thinner than that of the other portion, or if the porosity of the separator specific portion is higher than that of other portions, the ion conductivity of the portion is increased and the current is concentrated in that portion during charge / (SOC), which causes a large distribution in both directions. Such a distribution accelerates deterioration of the battery, which reduces the stability and reliability of the battery. Especially, it exhibits insufficient performance such as current leakage at a momentary high current momentary discharge (10 seconds).

The term nonwoven or nonwoven web as used herein refers to a nonwoven web or a nonwoven web in which the fibrous aggregate is treated chemically (e. G., By mixing the adhesive in fibers), mechanically or by suitable moisture and heat treatment, (Cloth) shape. The nonwoven web is bonded to the whole or a part thereof in a fusion-bonded manner. Such fusion can be achieved by heat at high temperature upon spinning of the spinning solution during the manufacturing process of the nonwoven web.

Accordingly, the present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to provide a nonwoven fabric substrate and an inorganic material which are designed to form uniformly the shape, structure and size of pores within a certain range by mixing two types of fibers having different thicknesses. An organic / inorganic composite porous coating layer containing particles and a polymeric binder resin. Here, the nonwoven fabric substrate may be composed of a single-stage nonwoven web. Or two or more nonwoven webs may be bonded to each other by a mechanical method by thermal welding. Hereinafter, for the sake of convenience in the description of the present invention, the filament yarns of the two types of filament yarns are referred to as first filament yarns and the coarse filament yarns are referred to as second filament yarns.

In a specific embodiment of the present invention, the first and second filament yarns differ in the average diameter of the filament yarns by 2 to 100 times, or 10 to 80 times, or 15 to 60 times, or 20 to 50, It is a ship. If the average diameter difference is not included in the above range, that is, if the average diameter is less than twice, the resistance reduction effect may be insignificant. If the average diameter of the two filament yarns exceeds 100 times, The same adverse effects can occur. Further, the smaller the deviation of the diameters of the first filament yarn and the second filament yarn, the better the pore and the uniformity of the size and the distribution of the pores. Preferably, the diameters of the first filament yarn and the second filament yarn are within a range within a deviation of an average diameter of 50%, preferably an average diameter of 30%, more preferably an average diameter of 20%.

According to a specific embodiment of the present invention, the first filament yarn and the second filament yarn are mixed in a weight percentage ratio of 20:80 to 50:50. If the mixing ratio is less than 20 wt%, the effect of reducing the resistance is insignificant. If the mixing ratio is more than 50 wt%, the tensile strength is lowered, and thus it is not suitable for use as a separator.

According to a specific embodiment of the present invention, the diameter of the first filament yarn may be selected from the range of 200 nm to 1000 nm for use as a separation membrane for a secondary battery, and the diameter of the second filament yarn may be selected from 1 to 10 Mu] m. As described above, the first filament yarn and the second filament yarn are advantageous in that the smaller the deviation in the diameter is, the better the property required as the separating film, and the second filament yarn is advantageous in that the first filament yarn It is appropriately selected within the range of 1 탆 to 10 탆 according to the thickness.

The nonwoven fabric substrate may have a long diameter (maximum diameter of pores) of pores to be formed in a range of about 0.2 μm to about 2 μm, preferably 0.2 μm to 1 μm. Preferably, the nonwoven substrate has pores having a major axis of pores of about 0.1 탆 to about 0.5 탆, preferably 0.1 탆 to 0.4 탆, more preferably 0.2 탆 to 0.3 탆, of about 50% or more , Preferably 80% or more. Nonwoven fabrics having a large number of pores having a major axis of less than about 0.2 탆 are difficult to manufacture. On the other hand, when the major axis of pores is larger than about 2 탆, the insulating property may be deteriorated due to the pore size. If the pores having the above-mentioned size range are formed to contain 50% or more of the total number of pores existing in the nonwoven fabric substrate, the pores are formed small and uniformly. Therefore, It is possible.

According to a specific embodiment of the present invention, the nonwoven fabric substrate is formed to have a thickness of 10 mu m to 35 mu m, preferably 10 mu m to 25 mu m, though it is not particularly limited. The separation membrane according to the present invention has an air permeability of about 50 s / 100 mL to 100 s / 100 mL. When the air permeability exceeds the above range, the movement of the electrolytic solution and the ion is lowered, and when the air permeability is lower than the above-mentioned range, the insulating property is lowered. In terms of the physical properties of the secondary battery separator, typically, the permeability refers to the time (e.g., second) (Gurley value) during which 100 mL of air passes through the separator having a thickness of 20 mu m, (Or discharge rate) in the cell performance, that is, the rate at which ions in a certain amount of electrolyte reach the both electrodes through the separator, that is, s / 100 mL As shown in FIG.

In the present invention, the first filament and the second filament may use the same or different polymer resin. In the present invention, the nonwoven fabric substrate is used as a separation membrane of a secondary battery. In consideration of thermal safety, the melting point or decomposition point of the polymer resin is preferably 200 ° C or higher.

In consideration of this point, the polymer resin may preferably include a polyolefin-based polymer resin. Non-limiting examples of the polyolefin-based fibers include high-pressure processed low-density polyethylene, linear low-density polyethylene, linear low-density polyethylene, or the like, which is a sole or copolymer of? -Olefins such as ethylene, propylene, 1-butene, 1-hexene, 1-pentene, ethylene / propylene random copolymer, ethylene / 1-butene random copolymer (so-called LLDPE), polyethylene terephthalate, high density polyethylene, polypropylene (propylene homopolymer), polypropylene random copolymer, -Butene random copolymer, and a propylene / 1-butene random copolymer, but are not limited thereto. These olefin-based polymers may be used alone or in combination of two or more.

As the polymer resin, a high heat-resistant polymer resin can be used. The high heat-resistant polymer resin is not particularly limited as long as the melting point is not lower than about 200 캜. Representative examples thereof include engineering plastic (EP) such as polyester resin, polyamide (PA) resin, polyimide (PI) resin and fluorine resin. It is not. According to a specific embodiment of the present invention, the first and second filaments can be used by mixing a polyolefin resin and a high heat-resistant polymer resin.

The first filament yarn and the second filament yarn according to the present invention may contain optional components such as an antioxidant, a heat stabilizer, a weather stabilizer, an antistatic agent, a slip agent, an antifogging agent, a lubricant, a dye, Various known additives such as natural oils, synthetic oils, and waxes may be added.

The nonwoven substrate of the separator according to the present invention can be produced by a process for producing a wet nonwoven fabric. First, a first filament yarn and a second filament yarn are produced. Next, the first and second filament yarns are dispersed in a quartz medium such as water to prepare a filament dispersion solution. At this time, the content of the first filament yarn can be adjusted to the above-mentioned range. The filament dispersion solution is then applied onto a papermaking wire or screen and the aqueous medium is removed using a vacuum pump. Thereafter, the sheet is pressed with a squeeze roll to obtain a sheet-like nonwoven web. When a nonwoven web is produced by a wet process, since the filaments of the first and second filament yarns are uniformly distributed in the filament web, the filament yarn can have excellent uniformity as compared with the dry nonwoven fabric method.

In addition, the nonwoven fabric substrate of the separator according to the present invention can be prepared by subjecting a polymer melt or a polymer dissolved in a solvent to a mixed solution. As the spinning method of the nonwoven substrate, there are spinning methods known in the art such as spun bonded, spun laced, melt blown, electro-spinning and the like But is not limited thereto.

Since the first nonwoven fabric of the separator according to the present invention is a mixture of the first filament yarn and the second filament yarn different in thickness, the spinning method is in particular in accordance with the method for producing a mixed nonwoven fabric. For example, after the polymer resin (A) for producing the first filament yarn and the polymer resin (B) for producing the second filament yarn are melted in separate extruders, the melted polymer resin is separately introduced into the detergent having a plurality of radiating holes, The resin (A) and the resin (B) may be simultaneously discharged from the different radiating apertures and the filament yarn may be deposited on one collector so that the first filament yarn and the second filament yarn are mixed. Here, the discharge amount of the polymer resin (A) for producing the first filament yarn and the polymer resin (B) for producing the second filament yarn can be appropriately adjusted so that the content of the first filament yarn is within the above-mentioned range. The deposited filament yarns form a mixed web of filament yarns through a web forming method known in the art, for example, a method of pressing and solidifying with a nip roll, etc., according to the end use purpose. At this time, the solidification can be performed under heating conditions for thermal fusion. The solidification is not particularly limited as long as the temperature of the solidified fibers and the temperature at which the fibers are melt-bonded to each other or the pressure range thereof are present. As a result, all or a part of the nonwoven web is fusion bonded (bonded) to each other. Such nonwoven webs can reinforce the bonds between the fibers through methods known in the art, such as needle punching, to form nonwoven fabrics having better tensile strength. The nonwoven fabric thus formed has a porous structure having a large number of pores, and the bonding strength between the fibers is greatly increased by fusion, and the tensile strength of the entire nonwoven fabric substrate is increased.

According to a specific embodiment of the present invention, the separation membrane of the present invention further comprises an organic / inorganic composite porous coating layer comprising a polymeric binder resin and inorganic particles on at least one side of the nonwoven substrate. The porous coating layer has pores formed due to the interstitial volume of the inorganic particles, and the inorganic particles are connected and fixed to each other by the binder resin.

The composition ratio of the inorganic particles and the binder polymer in the porous coating layer is, for example, in the range of 50:50 to 99: 1, more preferably 70:30 to 95: 5. When the content ratio of the inorganic particles to the binder polymer is less than 50:50, the content of the polymer is increased and the pore size and porosity of the porous coating layer may be reduced. If the content of the inorganic particles exceeds 99 parts by weight, the fillerability of the porous coating layer may be weakened because the content of the binder polymer is small. The loading amount of the porous coating layer on the nonwoven fabric substrate is preferably 5 to 20 g / m ² in consideration of the function of the porous coating layer and suitability for a high capacity battery. The pore size and porosity of the porous coating layer are not particularly limited, but the pore size is preferably in the range of 0.001 to 10 mu m, and the porosity is preferably in the range of 10 to 90%. The pore size and porosity mainly depend on the size of the inorganic particles. For example, when inorganic particles having a particle size of 1 탆 or less are used, pores formed also show about 1 탆 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 are 0.001 탆 or less and 10% or less, respectively, it can act as a resistive layer. If the pore size and porosity exceed 10 탆 and 90% respectively, mechanical properties may be deteriorated.

The binder polymer has a melting point or decomposition point higher than the melting point of the thermoplastic fine powder. The melting point or decomposition point of the binder polymer is preferably 200 ° C or higher. In particular, the melting point or decomposition point of the binder polymer is preferably higher than the melting point or decomposition point of the nonwoven fabric substrate in terms of thermal stability of the separator.

Such binder polymers include, for example, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate polyvinylidene fluoride, polymethylmethacrylate, polybutylacrylate, polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVdF-CTFE), polyacrylonitrile, polyvinylpyrrolidone, polyvinyl But are not limited to, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, Cellulose acetate propionate but are not limited to, polyvinylpyrrolidone, opionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxylmethylcellulose. methyl cellulose, or a mixture of two or more thereof, but is not limited thereto.

Although there is no particular limitation on the average particle diameter of the inorganic particles, it is preferably about 0.001 탆 to about 10 탆, preferably 0.01 탆 to about 1 탆, in consideration of formation of a coating layer having a uniform thickness and proper porosity. If the particle size of the inorganic particles is less than 0.001 탆, the dispersibility may be lowered, and if it is more than about 10 탆, the thickness of the coating layer may increase.

The kind of the inorganic particles is not particularly limited, but an inorganic particle selected from the group consisting of inorganic particles having a dielectric constant of about 5 or more, inorganic particles having a lithium ion transferring ability (in the case of a lithium secondary battery) Can be used. As the dielectric constant is about five or more inorganic particles is _{BaTiO 3, Pb (Zrx, Ti1} -x) O 3 (PZT, 0 <x <1), Pb 1 - x La x Zr 1 -y Ti y O 3 (PLZT , 0 <x <1, 0 <y <1), (1-x) Pb (Mg 1 / 3Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, 0 <x <1), 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 . But is not limited thereto. As the inorganic particles having lithium ion transferring ability, lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (LixTiy (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), lithium aluminum titanium phosphate _{(LixAlyTiz (PO 4) 3,} 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) x O y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate _{(Li x LayTiO 3, 0 <} x <2, 0 <y <3), lithium germanium Mani help thiophosphate _{(Li x Ge y P z S} w, 0 <x <4, 0 <y <1, 0 <z <1, 0 < w <5), lithium nitride _{(Li x Ny, 0 <x} <4, 0 <y <2), SiS 2 (Li x Si y S z, 0 <x <3, 0 <y <2, 0 <z <4) series glass and P ₂ S ₅ (Li _x P _y S _z , 0 <x <3, 0 <y < However, the present invention is not limited thereto.

The present invention also provides a secondary battery comprising the nonwoven fabric separator. The electrode to be applied together with the nonwoven fabric separator according to one aspect 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 Lithium composite 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 a secondary battery can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, (graphite) or other carbon-based materials and the like can be used. Non-limiting examples of the positive current collector include aluminum, nickel, or a combination thereof. Examples of the negative current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

The electrolyte which can be used in the secondary battery according to one aspect of the present invention is a salt having a structure such as A ⁺ B ^- , wherein A ⁺ is an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ It includes 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 - the salt containing ions consisting of the anionic, or a combination thereof, such as 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 Lactone (g-butyrolactone), or an organic solvent composed of a mixture thereof, but is limited thereto No.

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 porous separator according to an aspect 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 above-described embodiments. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Example

Membrane manufacturing

Fabrication of nonwoven substrates

7 g of polyethylene terephthalate fibers having an average diameter of about 800 nm and 13 g of polyethylene terephthalate fibers having an average diameter of about 4 m as a second filament yarn were prepared as first filament yarns. These were put into 1 L of distilled water and uniformly dispersed using a homogenizer to prepare a filament yarn dispersion solution. The filament yarn dispersion solution was applied on a screen and dried to obtain a nonwoven web. The nonwoven web was calendered to obtain a nonwoven fabric having a thickness of about 15 mu m.

Formation of organic / inorganic porous coating layer

PVdF-CTFE (polyvinylidene fluoride-chlorotrifluoroethylene copolymer) and cyanoethylpullulan were added to acetone at a weight ratio of 10: 2, respectively, and dissolved at 50 DEG C for about 12 hours or longer to obtain a polymer solution . Al ₂ O ₃ powder and BaTiO ₃ powder at a weight ratio of 9: 1 were added to a polymer solution prepared so as to have a weight ratio of polymer / inorganic particles = 10/90, The slurry was prepared by crushing and dispersing the particles. The average particle size of the inorganic particles of the thus prepared slurry was 600 nm on average. The above-prepared nonwoven fabric substrate having a thickness of 15 mu m was immersed in the prepared slurry for dip coating. The coating amount of the slurry was such that the thickness of the organic / inorganic composite coating layer finally formed was 5 탆 on each side of the substrate to make a total of 10 탆. The coated substrate was passed through a drier controlled to a temperature of 50 degrees to dry the solvent to complete the separator. The Gurley value of the completed membrane was good at 190 sec / 100 mL. The resistance was also good at 0.6 Ω.

Manufacture of batteries

Activated carbon as a negative active material and polyvinylidene fluoride as a binder were mixed in a N-methyl pyrrolidone solvent at a weight ratio of 96: 4 to prepare an anode slurry. The negative electrode slurry was coated on a Cu foil to a thickness of 14 μm to form a thin electrode plate. The electrode slurry was dried at 135 ° C for 3 hours or more and then pressed to manufacture a negative electrode.

LiCoO ₂ as a cathode active material, polyvinylidene fluoride as a binder and a carbon conductive material were dispersed in a N-methylpyrrolidone solvent in a weight ratio of 96: 2: 2 to prepare a cathode slurry. The positive electrode slurry was coated on platinum to a thickness of 60 mu m to form a thin electrode plate, dried at 135 DEG C for 3 hours or more, and rolled to prepare a positive electrode.

The thus fabricated negative electrode and the positive electrode were fabricated using the nonwoven fabric obtained above as a separation membrane, and an electrode assembly was prepared and placed in a battery case. Then, electrolytes mixed with ethylene carbonate and ethyl propionate at 70:30 were respectively injected to manufacture a secondary battery Respectively.

Comparative Example

Fabrication of Nonwoven Membrane

Instead of using 7 g of polyethylene terephthalate fibers having an average diameter of about 800 nm and 13 g of polyethylene terephthalate fibers having an average diameter of about 4 탆 as the first filament yarn, 20 g of polyethylene terephthalate fibers having an average diameter of about 4 탆 A nonwoven fabric separator was produced under the same conditions as those of the examples. The thickness of the nonwoven fabric obtained in the comparative example was about 15 mu m.

Manufacture of batteries

A battery was produced in the same manner as in Example except that the nonwoven fabric separating membrane obtained in Comparative Example was used.

Comparative experiment

Comparison of pore sizes

The pore size distribution of the nonwoven fabric separating membranes obtained in Examples and Comparative Examples was measured through a bubble point method (PMI Co., USA). Fig. 1 is a graph showing the distribution of pore sizes in the above-described embodiment and comparative example. According to the results, it was confirmed that the pore size of the separator according to the embodiment is mostly in the range of <0.5 μm. On the other hand, the separation membrane according to the comparative example was found to have a pore size ranging from 0.1 to 2 μm. FIG. 3 is a SEM photograph of the nonwoven fabric separating membrane according to the embodiment, and FIG. 4 is a SEM photograph of the nonwoven fabric separating membrane according to the comparative example. As can be seen from the above photographs, the nonwoven fabric separator of the Example had better porosity and higher uniformity in the size and distribution of pores than the Comparative Example.

Output performance experiment

Output performance experiments were performed on the membranes obtained in the examples and comparative examples as follows. After the battery is activated, the battery is charged for 10 seconds at a current of 1 ampere at a charge of 80%, and the voltage (V ') obtained by subtracting the voltage after 10 seconds from the voltage before applying the current is set to 1 ampere current (R = V '/ I), and the output is based on the resistance value. P (W) = I × V = (V' × V) / R Values were calculated. After 80% to 60% charge, the resistance was measured again in the order of 40% and 20%. FIG. 2 is a graph showing the comparison of the output performance test results of the battery using the separator obtained in Examples and Comparative Examples. FIG. As can be seen from FIG. 2, it was confirmed that both the charging and discharging periods were superior to those of the comparative example.

Claims (8)

Wherein a first filament yarn and a second filament yarn having different diameters are mixed with each other and an average diameter of the second filament yarn is 5 to 100 times an average diameter of the first filament yarn,
Inorganic composite porous coating layer formed on at least one side of the nonwoven substrate,
Wherein the first filament yarn and the second filament yarn are contained in a ratio of 20:80 to 50:50 wt%, the first filament yarn has a diameter of 200 nm to 1000 nm, and the nonwoven fabric substrate has 80% , And the diameter of the first filament yarn and the diameter of the second filament yarn are within a range of a deviation of the average diameter +/- 30%.
delete delete delete The method according to claim 1,
Wherein the nonwoven fabric substrate has a thickness of 10 mu m to 35 mu m.
The method according to claim 1,
Wherein the first filament yarn and the second filament yarn comprise a polyolefin-based polymer resin.
The method according to claim 1,
Wherein the organic / inorganic composite porous coating layer comprises inorganic particles and a polymer resin.
A secondary battery comprising the nonwoven fabric separator according to claim 1.

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