KR101419772B1 - 2-layer seperator for secondary cell with excellent heat-resisting property and its method - Google Patents

Abstract

The present invention relates to a method of manufacturing a two-layered separator for a secondary cell with an improved heat-resisting property and a separator manufactured in accordance to the method, and provides a method of manufacturing a two-layered separator for a secondary cell with an improved heat-resisting property whereby a nozzle block of an electro-spinning unit is divided into two spinning sections in a forward direction thereof; and polymers and inorganic polymers are continuously electro-spun in the spinning sections to manufacture a separator such that a multilayered separator having an improved heat-resisting property can be manufactured, thus the heat-resisting property of the separator, through which a thermal stability thereof can be improved, can be enhanced, and a separator manufactured according to the method. The method comprises the steps of: resolving and electro-spinning a first heat-resisting polymer filled in a first supply unit in an organic solvent to form a first heat-resisting polymer nanofiber; and electro-spinning a solution manufactured by resolving an inorganic polymer filled in a second supply unit in an organic solvent to an upper surface of the first heat-resisting polymer nanofiber to stack an inorganic polymer nanofiber.

Description

TECHNICAL FIELD [0001] The present invention relates to a heat-resistant / inorganic polymer two-layer separator for a secondary battery having improved heat resistance and an excellent heat-resisting property and its method,

The present invention relates to a heat-resistant / inorganic polymer double-layered separator for a secondary battery having improved heat resistance and a method for producing the same. More specifically, the first porous film having heat resistance characteristics and the second inorganic porous film are laminated in multiple layers, The separation membrane can be prevented from generating heat or the entire separator can be prevented from reaching the shutdown temperature, and a separation membrane produced thereby.

As consumers' demands have changed due to digitization and high performance of electronic products, market demand is changing due to the development of batteries with high capacity due to thinness, light weight and high energy density. In addition, in order to cope with future energy and environmental problems, development of hybrid electric vehicles and fuel cell vehicles is progressing actively, and it is required to increase the size of batteries for automobile power sources.

Secondary batteries, including high energy density and large capacity lithium ion secondary cells, lithium ion polymer batteries, and super capacitors (electric double layer capacitors and similar capacitors), must have a relatively high operating temperature range and should be continuously used at high rate charge and discharge The separator used in these cells is required to have higher heat resistance and thermal stability than those required in ordinary separators. In addition, it should have excellent cell characteristics such as rapid charge / discharge and high ion conductivity capable of coping with low temperature.

The separator is disposed between the anode and the cathode of the battery to insulate the electrolyte and maintain the electrolyte to provide a path for ion conduction. When the temperature of the battery becomes excessively high, a part of the separator melts to block the current, Lt; / RTI >

When the temperature rises further and the separator melts, a large hole is formed and a short circuit occurs between the anode and the cathode. This temperature is called SHORT CIRCUIT TEMPERATURE. In general, the separator should have a lower SHUTDOWN temperature and a higher short-circuit temperature. In the case of the polyethylene separator membrane, when the battery is abnormally heated, it shrinks at 150 ° C or higher and the electrode portion is exposed, which may cause a short circuit. Therefore, it is very important to have both a closing function and a heat resistance for a high energy density, large-sized secondary battery.

That is, there is a need for a separation membrane having excellent heat resistance, small heat shrinkage, and excellent cycle performance in accordance with high ion conductivity.

The porous nanofiber can be used for various purposes because it has a wide surface area and excellent porosity. For example, it can be used for a water purification filter, an air purification filter, a composite material, and a separator for a battery. Particularly, such a porous nanofiber can be applied to a membrane of a fuel cell for an automobile.

Conventional lithium ion polymer batteries using a conventional polyolefin separator and a liquid electrolyte such as a lithium ion secondary battery or a gel polymer electrolyte membrane or a polymer electrolyte gel coated on a polyolefin separator have a high energy density and a very high Lack. Therefore, the heat resistance required in a high-capacity, large-area battery such as an automobile does not satisfy the safety requirement.

In order to solve such a problem, US Patent Application Publication No. 2006-0019154A1 discloses a method in which a polyolefin-based membrane is impregnated with a polyamide, polyimide or polyamideimide solution having a melting point of 180 ° C or higher and then immersed in a coagulating liquid to extract a solvent, A heat - resistant polyolefin separator with a thin layer of heat - resistant resin is proposed. It has a small heat shrinkage, excellent heat resistance and excellent cycle performance. The heat-resistant thin layer is made porous through solvent extraction and the polyolefin separator used is limited to the use of an AIR PERMEABILITY of 200 sec / min or less.

Japanese Patent Application Laid-Open No. 2005-209570 also discloses a heat-resistant polyimide resin having a melting point of 200 ° C or higher, a polyimide, a polyether sulfone, a polyether ketone, and a polyetherimide having a melting point of 200 ° C or higher, The resin solution was applied on both sides of the polyolefin separating membrane, immersed in a coagulating solution, washed with water, and dried to show a polyolefin separating film having a heat resistant resin adhered thereto. In order to reduce the deterioration of ionic conductivity, a phase separator for providing porosity is contained in the heat resistant resin solution and the heat resistant resin layer is limited to 0.5-6.0 g / m 2.

However, the immersion in the heat-resistant resin restricts the movement of lithium ions by blocking the pores of the polyolefin separator, resulting in a decrease in charge-discharge characteristics, and even if the heat resistance is ensured, the demand for a large-capacity battery such as an automotive battery is insufficient. Even if the pore structure of the polyolefin porous membrane is not clogged due to the immersion of the heat resistant resin, the porosity of the polyolefin separator generally used is about 40%, and the pore size is also several tens of nanometers, which limits the ion conductivity for a large capacity battery .

U.S. Patent No. 6,447,958 discloses a slurry obtained by dissolving and dispersing a ceramic powder and a heat resistant nitrogen-containing aromatic polymer in an organic solvent as a support, a porous woven fabric such as polyolefin, rayon, vinylon, polyester, acrylic, polystyrene, nylon, A porous film or the like, and then removing the solvent. However, in the process of introducing the heat-resistant polymer layer, the porous heat-resistant resin layer including the application of the heat-resistant resin and the immersion, There is a problem that the manufacturing process of the semiconductor device is very complicated and the cost is greatly increased.

Japanese Patent Application Laid-Open Nos. 2001-222988 and 2006-59717 disclose polyaramid having a melting point of 150 占 폚 or higher, a woven fabric of polyimide, a nonwoven fabric, a cloth, and a porous film, and a polymer such as polyethylene oxide, polypropylene oxide, polyether, polyvinylidene The gel electrolyte is impregnated or coated to prepare a heat resistant electrolyte membrane. However, even in this case, the required heat resistance may be satisfied, but the ion transport in the support or the heat-resistant aromatic polymer layer is still limited in terms of ion conduction, similar to that of a separator or a gel electrolyte of a conventional lithium ion battery.

As a separator for a fuel cell currently in use, there is a perfluorosulfonic acid resin (Nafion, trade name) (hereinafter referred to as "Nafion resin") as a fluororesin. However, since the Nafion resin has a low mechanical strength, pinholes are generated when the Nafion resin is used for a long period of time, thereby deteriorating energy conversion efficiency. There is an attempt to increase the film thickness of the Nafion resin to reinforce the mechanical strength. However, in this case, there is a problem that the resistance loss is increased and the economical efficiency is lowered due to the use of the expensive material.

Therefore, the above-mentioned conventional patented techniques still do not satisfy the heat resistance and the ionic conductivity at the same time, and there is no mention of the shutdown function of the separator, High energy densities and large capacity batteries, such as batteries, are still unsatisfactory.

In order to solve the above problems, the present invention provides a method for preparing a separator capable of improving thermal stability by producing a nanofiber using a heat-resistant polymer and an inorganic polymer, and a separator prepared thereby.

The present invention is characterized in that a nozzle block having a nozzle of an electrospinning device is divided into two sections in the horizontal direction and is provided with a first feeding device for feeding the polymer to each divided section and a second feeding device, A method for producing a separation membrane for spinning polymer, the method comprising: forming a heat-resistant polymer nanofiber by electrospinning a solution prepared by dissolving a heat-resistant polymer in an organic solvent in a first feeding device of the electrospinning device; And a step of spinning a solution prepared by dissolving an inorganic polymer in an organic solvent in a second supply device of the electrospinning device onto the first heat-resistant polymer nanofibers to laminate the inorganic polymer nanofibers And a manufacturing method thereof.

In addition, the heat-resistant polymer of the present invention is at least one polymer selected from the group consisting of polyimide, polyacrylonitrile, meta-aramid, and polyvinylidene fluoride. In the two-layer separator for a secondary battery, And an inorganic polymer nanofiber layer formed on the upper surface of the nanofiber. The present invention also provides a manufacturing method of a heat-resistant / inorganic polymer bilayer separator for a secondary battery.

The two-layer separator for a secondary battery according to the present invention has a blocking function to prevent a short circuit phenomenon. The battery is excellent in stability even in the event of thermal runaway, and the wettability is improved. Polyimide porous nanofibers having such excellent physical properties can be used for an electrolyte membrane for a fuel cell or a separator for a secondary battery, which is required to have a light weight, a high efficiency, and a high stability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a method for producing a porous separator of the present invention. FIG.

A method of preparing a two-layer porous separator by electrospunning the heat-resistant polymer and the inorganic polymer of the present invention will be described.

Wherein the heat resistant polymer is at least one selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer or a composite composition thereof, polyamide, polyimide, polyamideimide, poly (meta-phenyleneisopthalamide) Is at least one material selected from the group consisting of polychlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride-acrylonitrile copolymer, and polyacrylamide.

Examples of usable solvents include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, cyclohexane, water or a mixture thereof. no.

In the present invention, the separation membrane among the heat-resistant polymers is most preferably polyimide, polyacrylonitrile, meta-aramid, or polyvinylidene fluoride.

The electrolyte membrane for a fuel cell should contain ionic conductors to smoothly transfer ions. In order for these ions to move smoothly through the electrolyte membrane, the ion conductor must be evenly filled throughout the nanofiber. However, if the pore is too small or too large, the ion conductor may become unevenly charged, resulting in a problem that the ion conductivity is lowered. That is, the ion conductor can be impregnated smoothly in the nanofiber only if there are many pores having a specific pore size. In other words, if the pore size is too small, the ion conductor may not be impregnated smoothly, whereas if the pore size is too large, the ion conductor may be excessively impregnated.

Therefore, it is preferable that the size of the pore size in which such ion conductor can be smoothly impregnated into the pore of the nanofiber is 1.5 mu m and not exceeded the range of +/- 0.2 mu m.

In the heat-resistant polymer of the present invention, the polyimide nanofiber is synthesized from poly (amic acid) (PAA), mixed with a mixture of tetrahydrofuran (THF) and dimethylacetamide (DMAc) ) To prepare polyamic acid dope, and PAA nanofiber separation membrane was prepared by electrospinning. Polyimide (PI) nanofibers were prepared on the polyolefin substrate by imidization, The slurry prepared by adding the inorganic particles and the polyimide-affinity polymer resin to the acetone on the polyimide nanofiber can be coated by the casting method to more firmly adhere the inorganic coating layer and improve the heat resistance stability and wettability of the separator I will.

The PI is prepared by a two-step reaction.

In the first step, polyamic acid is prepared by adding dianhydride to a reaction solution in which diamine is dissolved. In order to increase the degree of polymerization, the reaction temperature, the water content of the solvent, And purity control. As the solvent used in this step, organic polar solvents such as dimethylacetamide (DMAc), dimethylformamide (DMF) and en-methyl-2-pyrrolidone (NMP) are mainly used. Examples of the anhydride include pyromellitic dianhydride (PMDA), benzophenonetetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic anhydride (4,4'-oxydiphthalic anhydride) ODPA), biphenyltetracarboxylic dianhydride (BPDA), and bis (3,4'-dicarboxyphenyl) dimethylsilane dianhydride (SIDA). One can be used. Examples of the diamine include 4,4'-oxydianiline (ODA), p-penylene diamine (p-PDA) and o-penylenediamine o-PDA) may be used.

Reaction 1. Preparation of polyamic acid

The second step is the dehydration and ring-closing reaction step of producing polyimide from polyamic acid as the following four methods.

In the re-impregnation method, a polyamic acid solution is added to an excessive amount of a poor solvent to obtain a solid polyamic acid. As the re-precipitation solvent, water is mainly used, but toluene or ether is used as a co-solvent.

The chemical imidization method is a method in which a imidization reaction is chemically performed using a dehydration catalyst such as acetic anhydride / pyridine, and is useful for producing a polyimide film.

The thermal imidization method is a method in which the polyamic acid solution is heated to 150 to 200 ° C to thermally imidize it. In the simplest process, the crystallization degree is high, and the amine exchange reaction occurs when the amine type solvent is used. have.

In the isocyanate method, diisocyanate is used instead of diamine as a monomer, and when the monomer mixture is heated to a temperature of 120 ° C or higher, a polyimide is produced while CO ₂ gas is generated.

Reaction formula 2. Preparation of polyimide

The electrospinning device includes a spinning liquid main tank for storing a spinning solution, a metering pump for supplying a spinning solution in a fixed amount, a nozzle block for combining a plurality of tubular nozzles composed of a plurality of pins in block form and discharging the spinning solution in a fiber form, A collector for accumulating short fibers emitted at a position corresponding to the nozzle block, a voltage generating device for generating a high voltage, and a spinning solution discharging device connected to the top of the nozzle block.

The method of preparing the nanofibers by electrospinning the polyimide of the present invention is performed through the following process.

First, a spinning solution is prepared by dissolving polyimide in a mixed solvent of tetrahydrofuran (THF) / dimethylacetamide (DMAc) (THF / DMAc), and the polyimide spinning solution is stored, Weigh with a separate weighing pump and supply to the spinning solution drop unit by weighing.

The polyvinylidene fluoride (PVDF) polymer electrolyte is prepared by preparing a polymer matrix to have a submicron porosity and then injecting an organic electrolytic solution into these small pores. The polymer electrolyte is excellent in compatibility with organic electrolytes, Is advantageous in that it can be used as a safe electrolyte without being leaked. Since the organic solvent electrolyte is injected later, the polymer matrix can be produced also in the air.

The weight average molecular weight (Mw) of the polyvinylidene fluoride resin is not particularly limited, but is preferably 10,000 to 500,000, more preferably 50,000 to 500,000.

When the weight average molecular weight of the polyvinylidene fluoride resin is less than 10,000, the nanofibers constituting the nanofibers can not obtain sufficient strength. When the molecular weight exceeds 500,000, the solution is not easily handled and the uniformity of the nanofiber is deteriorated. It becomes difficult to obtain.

Polyacrylonitrile (PAN) resins are copolymers made from a mixture of acrylonitrile and monomers that make up the majority. Other monomers that are frequently incorporated are butadiene styrene, vinylidene chloride, or other vinyl compounds. Of course, the same acrylic fiber contains at least 85% acrylonitrile, and mode acrylic contains 35-85% acrylonitrile. The inclusion of other monomers can bring together the desired properties, such as increasing the affinity of the fiber to the dye.

The polymerization degree of the polyacrylonitrile is 1,000 to 1,000,000, preferably 2,000 to 1,000,000. If the degree of polymerization is too low, the efficiency of the battery tends to decrease due to the dissociation of the electrode from the current collector as the cycle is progressed as the electrolyte dissolves or swells in the carbonate electrolyte. If the degree of polymerization is too high, There is a disadvantage that it is difficult to handle by increasing the viscosity.

Next, a spinning solution is prepared by dissolving meta-aramid in dimethylformamide (DMF) or dimethylacetamide (DMAc) solvent. In addition to the above, it is possible to use a resin such as a polyester resin, an acrylic resin, a phenol resin, an epoxy resin, a nylon resin, a poly (glycolide / L-lactide) copolymer, a poly (L-lactide) resin, a polyvinyl alcohol resin, Can be used. As the spinning solution, any of the resin melt or solution may be used.

The specific gravity of the meta-aramid is 1.3 to 1.4, and the weight average molecular weight is more preferably 300,000 to 1,000,000. The meta-aramid is the first highly heat-resistant aramid fiber that can be used at 350 ° C for a short time and 210 ° C for continuous use. When exposed to temperatures above this temperature, it is carbonized without melting or burning like other fibers. Above all, unlike other products that are flame retarded or refractory treated, they do not emit toxic gases or harmful substances even when carbonized, and thus they have excellent properties as eco-friendly fibers.

In addition, since the molecules constituting the fibers themselves have a very rigid molecular structure, the meta-aramid is not only strong in its inherent strength, but also improves the strength as the molecules are easily oriented in the fiber axis direction in the spinning stage .

The inorganic polymer may be selected from the group consisting of a siloxane group alone or a siloxane group and monomethacrylate, vinyl, hydride, distearate, bis (12-hydroxy-stearate), methoxylate, ethoxylate, propoxylate, diglycidyl A polymer comprising a bonding group selected from the group consisting of ether, monoglycidyl ether, monohydroxy, bis (hydroxyalkyl), chlorine, bis (3-aminopropyl), and bis ((aminoethyl-aminopropyl) dimethoxysilyl) Can be used.

As a most preferable inorganic polymer spinning method, a spinning solution in which an inorganic polymer is dissolved in an acetone solvent is first prepared, the spinning solution of the inorganic polymer is stored in a spinning solution main tank, weighed by a separate weighing pump, Supply.

An example of the electrospinning device used in the present invention will be described as follows.

The electrospinning device is composed of a main tank for storing a flushing liquid, a metering pump for supplying a flushing liquid, a nozzle block for discharging the flushing liquid in a fiber form, and a plurality of tubular nozzles, A collector for accumulating short fibers emitted at a position corresponding to the nozzle block, a voltage generator for generating a high voltage, and a first and a second supply device for supplying a spinning solution for each section between the metering pump and the nozzle block .

The polyimide and the inorganic polymer spinning solution are respectively stored in spinning liquid main tanks 1 and 2 of the electrospinning liquid of the present invention. The first and second feeding devices are designed to have a generally closed cylindrical shape, And supplies the spinning solution, which is injected into each of the sections, to the respective sections. The nozzle block is divided into two sections, and the first and second feeders are provided in each section, and the spinning solution uses a polyimide solution as the first solution and a solution in which the inorganic polymer is dissolved in the solvent as the first solution. The length of the section defined by the nozzle block can be adjusted according to the thickness of each layer constituting the separation membrane.

Next, a method for manufacturing a two-layer separator using the electrospinning apparatus of the present invention will be described.

First, the heat-resistant polymer filled in the spinning liquid tank and the spinning solution of the inorganic polymer are weighed by a metering pump, and the heat-resistant polymer is supplied to the first feeding device and the spinning solution of the inorganic polymer is supplied to the second feeding device. Then, in the nozzle block, the spinning liquid is discharged through a nozzle to a collector at a lower portion where a high voltage is applied, thereby manufacturing a nanofiber. At this time, the spinning nozzle is disposed above a grounded collector of a conveyor type moving at a constant speed Arranged in two rows at intervals along the advancing direction of the collector, and a plurality of spinning nozzles are provided for each column.

The polymer spinning solution discharged sequentially from the two-row spinning nozzle will be described in detail. In the first supply device, the heat-resistant polymer spinning solution is discharged into the nanofiber while passing through the spinning nozzle charged by the high voltage generator, And the heat-resistant polymer nanofibers irradiated on the collector move in a second section at a constant speed to sequentially laminate the inorganic polymer nanofibers to produce a two-layer separator.

At this time, the grounded collector can be controlled to move in one direction and then a continuous process of forming a two-layer separation membrane is possible. Such a process simplifies the manufacturing process of the separation membrane and increases the production speed.

The thickness of the polymer membrane, the diameter of the fiber, the shape of the fiber, and the mechanical characteristics of the separation membrane can be arbitrarily controlled by controlling the electrospinning process conditions such as the intensity of the applied voltage, the kind of the polymer solution, the viscosity of the polymer solution, Can be adjusted.

 The preferred electrospinning process conditions are such that when the spinning solution transferred to the spinning liquid supply tube is discharged to the collector through the multi tubular nozzle to form the fibers, the nanofibers electrospun from the multi-tubular nozzles are ejected from the air- It spreads widely and is collected on the collector to widen the collecting area and to make the density of the particles uniform. The excess flushing liquid which is not fibrous in the multistage nozzle is collected in the overflow removing nozzle and moved to the flushing liquid supply plate through the temporary storage plate of the overflow liquid.

When manufacturing nanofibers, it is preferable that the speed of air in the air supply nozzle is 0.05 m to 50 m / sec, more preferably 1 to 30 m / sec. If the velocity of the air is less than 0.05 m / sec, the collecting area of nanofibers is not so low and the collecting area is not greatly improved. If the velocity of the air exceeds 50 m / sec, And the more serious problem is attached to the collector in the form of coarse tuft, not the nanofiber, so that the ability to form nanofibers is remarkably deteriorated.

In addition, the spinning solution which is excessively supplied to the top of the nozzle block is forcibly transferred to the spinning liquid main tank by the spinning solution discharging device.

At this time, in order to promote the formation of the fiber by the electric force, a voltage of 1 kV or more, more preferably 20 kV or more, generated by the voltage generator is applied to the conductive plate and collector provided at the lower end of the nozzle block. It is more advantageous in terms of productivity to use an endless belt as the collector. The collector preferably reciprocates a predetermined distance in the left and right directions to uniform the density of the nanofibers.

The manufacturing apparatus can increase the collecting area to uniform the density of the nanofibers and effectively prevent the droplet phenomenon, thereby improving the quality of the nanofibers and enhancing the fiber-forming effect by the electric force, Can be mass-produced. In addition, the width and the thickness of the nanofibers can be freely changed and adjusted by arranging the nozzles composed of a plurality of pins in block form.

In addition, when the heat-resistant polymer is spun as described above, it is most preferable to spin the polymer under environmental conditions of a temperature range of 30 to 40 DEG C and a humidity of 40 to 70% depending on the polymer material.

The total diameter of the two-layer separation membrane of the radiated nanofiber of the present invention is preferably 30 to 2000 nm, more preferably 50 to 1500 nm.

The porosity of the two-layer separation membrane is preferably 40 to 80%, and as the fiber diameter is smaller, the pore size becomes smaller and the pore size distribution becomes smaller. In addition, since the specific surface area of the fibers is increased as the diameter of the fibers is smaller, the ability to lyse the electrolyte increases and the possibility of leakage of the electrolyte decreases.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the embodiments are only examples of the present invention, and the scope of the present invention is not limited thereto.

[Example 1]

In the first section, polyacrylonitrile (Korea-Japan synthesis) having a weight average molecular weight of 157,000 was dissolved in a dimethylformamide (DMF) solvent to prepare a spinning solution. In the second section, polysiloxane having a number average molecular weight of 50,000 (DOW CORNING MB50-010) is dissolved in an acetone solvent to prepare a 20 mass% polysiloxane dope. A polyacrylonitrile nanofiber having a thickness of 5 탆 was formed under the conditions of a distance of 40 cm between the electrode and the collector, an applied voltage of 15 kV, a spinning solution flow rate of 0.1 mL / h, a temperature of 22 캜 and a humidity of 20% And the inorganic polymer nanofiber is spinned in the second section to a thickness of 5 占 퐉 on the upper layer of the polyacrylonitrile nanofiber to form a two-layer separator.

[Example 2]

In the first section, a methacrylamide (EI du Pont de Nemours and Company) having a weight average molecular weight of 300,000 was dissolved in a dimethylformamide (DMF) solvent to prepare a spinning solution. In the second section, a number average molecular weight The polysiloxane having a molecular weight of 50,000 (DOW CORNING MB50-010) was dissolved in an acetone solvent to prepare a 20 mass% polysiloxane dope. A 5-μm-thick meta-aramid nanofiber was formed under the electrospinning conditions of a distance of 40 cm between the electrode and the collector, an applied voltage of 15 kV, a spinning solution flow rate of 0.1 mL / h, a temperature of 22 ° C. and a humidity of 20% 2, a two-layer separator is formed by spinning the inorganic polymer nanofibers to a thickness of 5 탆 on the upper layer of the meta-aramid nanofibers.

[Example 3]

In the first section, polyvinylidene fluoride (KYNAR 741) having a weight average molecular weight (Mw) of 500,000 was dissolved in dimethylacetamide (DMAc) solvent to prepare a spinning solution. In the second section, polysiloxane Acetone solvent to prepare a 20 mass% polysiloxane dope. A polyvinylidene fluoride nanofiber having a thickness of 5 탆 was formed under the conditions of a distance of 40 cm between the electrode and the collector, an applied voltage of 15 kV, a spinning liquid flow rate of 0.1 mL / h, a temperature of 22 캜 and a humidity of 20% And the inorganic polymer nanofibers are spun in the upper section of the polyvinylidene fluoride nanofibers so as to have a thickness of 5 탆 to form a two-layer separator.

[Comparative Example 1]

Polyacrylonitrile was dissolved in a DMF solvent to prepare a spinning solution. Electrospinning conditions were 40 cm, an applied voltage of 15 kV, a spinning liquid flow rate of 0.1 mL / h, a temperature of 22 캜 and a humidity of 20% Thick polyacrylonitrile nanofiber is produced.

[Comparative Example 2]

The meta-aramid was dissolved in a DMF solvent to prepare a spinning solution. Electrospinning conditions of a distance of 40 cm between the electrode and the collector, an applied voltage of 15 kV, a spinning solution flow rate of 0.1 mL / h, a temperature of 22 캜 and a humidity of 20% To produce a meta-aramid nanofiber.

[Comparative Example 3]

(PVdF) was dissolved in dimethylacetamide (DMAc) solvent to prepare a spinning liquid. The distance between the electrode and the collector was 40 cm, the applied voltage was 15 kV, the spinning liquid flow rate was 0.1 mL / h, the temperature was 22 캜, To prepare a polyvinylidene fluoride nanofiber having a thickness of 10 탆 in an electrospinning condition of 20%.

- Evaluation of Heat Shrinkage of Membrane -

The separation membranes of Examples 1 to 3 and Comparative Examples 1 to 3 were cut into 3 cm x 3 cm, and then stored at 150 ° C for 30 minutes, and the heat shrinkage was evaluated.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Heat shrinkage (%) 3 2 3 9 7 9 Thickness (㎛) 10 10 10 10 10 10

As described above, the heat resistant polymer / inorganic polymer bilayer separator provided by the present invention has improved heat stability compared to the heat resistant separator.

Claims (5)

A nozzle block having a nozzle of the electrospinning device is divided into two sections in the horizontal direction and is provided with a first feeding device for feeding the polymer to each divided section and a second feeding device for feeding the polymer onto the collector, In the method of producing a separating membrane for spinning,
Forming a heat-resistant polymer nanofiber by electrospinning a solution prepared by dissolving a heat-resistant polymer in an organic solvent in a first supply device of the electrospinning device, on a collector;
Depositing a solution prepared by dissolving an inorganic polymer in an organic solvent in a second feeding device of the electrospinning device, onto the first heat-resistant polymer nanofibers to laminate the inorganic polymer nanofibers;
And a second layer separating film for a secondary battery having improved heat resistance. The method according to claim 1,
Wherein the method of electrospinning a polymer on a collector is a bottom-up electrospinning method. The method according to claim 1,
Wherein the heat-resistant polymer is at least one polymer selected from the group consisting of polyimide, polyacrylonitrile, meta-aramid, and polyvinylidene fluoride. The method according to claim 1,
Wherein the inorganic polymer is a silane group or siloxane group alone polymer or a copolymer polymer of silane group or siloxane group. delete

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