KR100858215B1 - Electrochemical device with high stability at high temperature and over-voltage - Google Patents

Abstract

The present invention (a) a porous substrate having pores; And (b) a separator comprising a foaming agent-containing coating layer formed on the surface of the substrate or a part of the pores, wherein the foaming agent releases a gas other than oxygen at a temperature T higher than the normal operating temperature range of the battery. And it provides a method of manufacturing the same, the electrochemical device comprising the separator.

In the present invention, by using a blowing agent that releases a large amount of inert gas in the temperature range above the normal operating temperature of the battery as a coating component of the separator, it is possible to improve the safety of the battery during overcharge and high temperature storage. .

Separator, Foaming Agent, Azo System, Safety, Electrochemical Device, Lithium Secondary Battery

Description

ELECTROCHEMICAL DEVICE WITH HIGH STABILITY AT HIGH TEMPERATURE AND OVER-VOLTAGE

The present invention relates to a separator and an electrochemical device having the electrode, which can provide excellent safety even if the battery internal temperature rises abnormally due to external or internal factors, and more particularly, emits a large amount of inert gas at high temperature. Separator that prevents contact with oxygen necessary for ignition by increasing the internal pressure due to released gas and enables early venting by preventing blowing and / or ignition during overcharge and high temperature storage And it provides a method for manufacturing the same, the electrochemical device having improved safety by having the separator.

In general, the stability of a lithium secondary battery using a flammable non-aqueous electrolyte is caused to ignite due to various causes, the stability is drastically reduced. Among the various known causes, the first reaction is caused by shrinkage of the separator interposed between the positive electrode and the negative electrode to prevent short of the positive electrode. Polyethylene separators are currently used in the melting range of 120 to 130 ℃ and thus accompanied by the shrinkage of the separator, and eventually the short-circuited by contacting the cathode and the anode at the corners, resulting in a large amount of current flow The internal temperature of the battery continuously increases due to the supply of thermal energy, which causes the battery to ignite as it reaches the temperature at which the electrolyte decomposes.

In order to solve this problem, a solution through the organic electrolyte additive has been proposed. For example, U. S. Patent No. 6,074, 776 discloses a method of controlling the flow of current through an increase in electrode resistance by making an insulating layer on the surface of the anode at high temperature, wherein the aromatic monomer additive introduced is used to cause a polymerization reaction in a high voltage state. It was. However, there is still a risk of ignition of the battery due to electrolyte decomposition when the temperature rises.

In Japanese Patent Laid-Open No. 2002-157979, it is excellent in thermal stability and a flame retardant magnesium alloy having a ignition temperature of 550 ° C. or higher is added to a nonaqueous electrolyte to prevent battery from igniting and burning even when the battery temperature rises. The method is disclosed. However, even in this case, even though the magnesium alloy can absorb some heat, it is not possible to absorb all the heat inflows due to the continuous temperature rise, so there is a risk of ignition.

In Japanese Patent Laid-Open No. 194-150975, a method of pressurizing and charging an electrolyte solution with carbon dioxide is used to easily release the electrolyte solution together with carbon dioxide when the temperature of the battery rises abnormally. However, when the electrolyte is sucked into the inner pores of the separator or the inside of the electrode, the gas ignition alone is not easily released to the outside, so the risk of battery ignition due to decomposition of the electrolyte is still not solved.

Japanese Patent Laid-Open No. 1999-317232 proposes a method of flame retarding an electrolyte solution for a lithium secondary battery by adding a phosphate flame retardant such as trialkyl phosphate, trimethyl phosphate, or dimethyl phosphate to the electrolyte solution. However, in the case of halogen-based flame retardants that release inert gas to prevent contact with oxygen or phosphate-based flame retardants that melt by heat and coat the surface of the object to prevent contact with oxygen, a fire already occurs and propagates to the remaining electrolyte. In the state it was difficult to evolve. In addition, when a large amount of flame retardant is to be used to exert a safety improvement effect, the ion conductivity is lowered, which inevitably leads to deterioration of battery characteristics, thereby limiting the input amount of the material.

In view of the above-described problems, the present inventors have released a large amount of gas other than oxygen at a temperature T higher than the normal operating temperature range of the battery, preferably higher than the normal temperature range of the battery and lower than the shrinkage generating temperature of the separator. When the blowing agent is introduced into the separator, the temperature rises rapidly due to the membrane shrinkage caused by the abnormal temperature rise of the battery due to external or internal factors, the internal short circuit caused by the contact of the positive electrode, and the high current flow. It was first conceived that the thermal runaway phenomenon is prevented. In fact, using a blowing agent as the coating component of the separator, the blowing agent coated at a temperature higher than the normal operating temperature of the cell, such as around 110 ° C, releases a large amount of inert gas to increase the internal pressure, enabling premature ignition, thereby prematurely firing. Not only can it be prevented, but even if it is not vented, the released inert gas reduces the concentration of oxygen, the ignition element, and the contact between oxygen and the electrolyte gas is prevented inherently, thereby suppressing battery ignition and explosion by the flammable electrolyte gas and thereby It was confirmed that the effect of improving the safety of the battery was excellent.

Accordingly, an object of the present invention is to provide a separation membrane containing a blowing agent capable of achieving the above-mentioned safety improvement effect, a manufacturing method thereof, and an electrochemical device having the separation membrane.

The present invention (a) a porous substrate having pores; And (b) a separator comprising a foaming agent-containing coating layer formed on the surface of the substrate or a part of the pores, wherein the foaming agent releases a gas other than oxygen at a temperature T higher than the normal operating temperature range of the battery. And it provides an electrochemical device, preferably a lithium secondary battery having the separator.

In addition, the present invention comprises the steps of (a) adding a blowing agent and a binder polymer to a solvent or a dispersion medium to prepare a blowing agent-containing binder solution; And (b) coating the solution on the surface of the porous substrate having the pores or a part of the pores and then drying the solution.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention is characterized by using a blowing agent (보조) used as a coating component of the separator even if not applied to the conventional cell or used to form a pore structure by thermal decomposition.

Conventional blowing agents have been used for the purpose of reducing the amount of raw materials used in impact or by adding a rubber, polyurethane, EVA and the like to decompose at the processing temperature during extrusion or injection processing to release a large amount of gas to form bubbles. However, in the present invention, the blowing agent is used for the purpose of instantaneously decomposing in a narrow temperature range to eject a large amount of inert gas and to raise the pressure inside the battery.

When the blowing agent having the above characteristics is used as a separator component, it may exhibit an effect of improving the safety of the battery.

In other words, when the temperature of the battery rises abnormally due to internal or external factors such as high temperature storage or overcharging, the decomposition reaction of the electrolyte, the generation of flammable gas by the reaction between the electrolyte and the electrode, the internal short circuit caused by the shrinkage of the separator, etc. This causes the battery to ignite and explode. In order to solve such a problem, an electrolyte additive such as a monomer additive and a flame retardant to form an insulating layer was used, but the problem of deterioration of fundamental safety of the battery was not solved, and this resulted in deterioration of battery characteristics.

In contrast, in the present invention, by using a blowing agent that releases a large amount of a gas, such as an inert gas, except for oxygen (O ₂ ), which is one of the ignition elements, at a temperature higher than the normal operating temperature range of the battery, contact with oxygen, which is a ignition factor, is blocked. It is possible to fundamentally solve the occurrence of ignition of the battery.

In addition, the blowing agent coated on the surface of the separator absorbs and decomposes heat inside the battery, thereby partially suppressing the shrinkage of the separator through temperature rise control, thereby suppressing internal short circuit caused by contact between the positive electrode and the negative electrode. In addition, the separator may cause a temperature drop by operating the vent through an increase in the internal pressure of the battery due to the gas generated from the blowing agent in a temperature (T) range above the normal operating temperature.

In addition, in the present invention, since the blowing agent is added to the separator instead of the electrolyte solution additive, it does not affect the lithium ion conductivity dissolved in the electrolyte solution, thereby preventing performance degradation of the battery.

Through such a complex action, it is possible to achieve an excellent safety improvement effect of the battery.

Blowing agent capable of achieving the above-mentioned action can be used as a coating component of the membrane, wherein the blowing agent can decompose instantly in a specific temperature range to release a large amount of gases other than oxygen. Conventional blowing agents known in the art can be used without limitation.

The temperature (T) for decomposing the blowing agent to release a large amount of gas is not particularly limited as long as the temperature is higher than the normal operating temperature of the battery, in particular, it is higher than the normal operating temperature range of the battery, and shrinkage of the porous substrate provided in the battery A lower temperature range than the temperature at which it occurs is preferred. In one example, the temperature ranges from 100 to 120 ° C.

In addition, there is no particular restriction as to the gas component to be released by the thermal decomposition of the blowing agent as long as it is not an oxygen ignition element, but preferably an inert gas such as N ₂ , He, Ne, Ar, Kr, Xe or a mixture thereof. Do.

Non-limiting examples of the blowing agent that can be used include azo (azo, -N = N-)-based compounds, preferably azobis 2-cyanobutane (azobis (2-cyanobutane)) series represented by the formula Compound.

Since the azobis 2-cyanobutane series blowing agent rapidly releases a large amount of nitrogen, such as about 25 to 350 ml / g, in the range of 110 to 120 ° C., the safety improvement effect of the battery described above can be sufficiently satisfied. In addition to the foaming agent of the above components, as long as the above conditions can be satisfied to improve the safety of the battery, the components, forms, and the like thereof are not particularly limited.

The blowing agent-containing coating layer contains, in addition to the blowing agent, binder polymers conventional in the art. Non-limiting examples thereof include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, and polymethyl methacrylate. Polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer, polyethylene oxide Cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, Cyanoethylcellulose, cyanoethyl water Cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, or mixtures thereof. .

There is no particular limitation as to the constituent ratio of the blowing agent and the binder polymer, but if possible, the blowing agent is preferably included in the range of 0.5 to 50 parts by weight based on 100 parts by weight of the binder polymer. If the blowing agent is used less than 0.05 parts by weight, the desired safety improvement effect may be insignificant. If it exceeds 10 parts by weight, the blowing agent may be easily peeled off on the porous substrate, thereby preventing the desired safety improvement effect.

The substrate into which the blowing agent is to be introduced is not particularly limited as long as it is a porous substrate having conventional pores known in the art. Non-limiting examples thereof include polyolefin series such as polyethylene and polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, Polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfidro, ethylenenaphthalene or Mixtures thereof and the like.

According to the present invention, a method of preparing a separator including a blowing agent as a coating component of the separator is not particularly limited, but a preferred embodiment thereof includes (a) a blowing agent-containing binder solution by adding a blowing agent and a binder polymer to a solvent or a dispersion medium. Preparing a; And (b) coating the solution on the surface of the porous substrate having a pore or a part of the pore, followed by drying.

Hereinafter, an example of a method of coating the blowing agent on the separator will be described in detail.

First, 1) a binder (eg, polyvinylidene fluoride (PVDF)) is added to a solvent or a dispersion medium (eg, NMP (N-methyl pyrroridone) to prepare a binder solution.

At this time, the binder is appropriately added in 5 to 20 parts by weight (weight ratio) based on 100 parts by weight of the solvent or dispersion medium, but is not limited thereto.

In addition, the solvent or dispersant used to prepare the binder solution may be any of conventional solvents used in the art, and in particular, in order not to cause thermal decomposition of the blowing agent by solvent drying, Solvents with low boiling points are preferred. Non-limiting examples thereof include organic solvents such as N-methylpyrrolidone, acetone, dimethylacetamide, or dimethylformaldehyde, inorganic solvents such as water, or mixtures thereof. The amount of the solvent may be sufficient to dissolve and disperse the active material, the conductive material, the electrode binder, and the adhesion enhancing additive in consideration of the coating thickness of the electrode slurry and the production yield. The solvents are removed by drying after coating the electrode slurry on a current collector.

2) After the blowing agent is added to the prepared binder solution, mixed, and completely dispersed, the membrane is prepared by applying and drying it on a porous substrate having pores.

The blowing agent is appropriate to add 0.5 to 50 parts by weight relative to the binder, but is not limited thereto. In addition, the method of coating the mixture of the blowing agent and the binder on the porous substrate may use a conventional coating method known in the art, for example, dip coating, die coating, roll coating, Various methods, such as a comma coating or a mixing method thereof, can be used. In addition, the binder solution containing the blowing agent may be coated by impregnating the porous substrate or spraying the solution with a nozzle. In this case, the separator may be coated in a range of 0.1 to 30 mg / cm ² by a blowing agent, but is not limited thereto. When the mixture of the blowing agent and the binder polymer is coated on the porous substrate, it may be carried out on both sides of the porous substrate or may be selectively carried out only on one side.

The present invention also provides an electrochemical device comprising an anode, a cathode, a separator coated with a blowing agent, and an electrolyte.

Electrochemical devices include all devices that undergo an electrochemical reaction, and specific examples thereof include all kinds of primary, secondary cells, fuel cells, solar cells, or capacitors. In particular, a lithium secondary battery is preferable among secondary batteries, and non-limiting examples thereof include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

The electrochemical device may be manufactured according to a conventional method known in the art, and for example, by injecting an electrolyte after assembling the separator coated with the above-described blowing agent between the positive electrode and the negative electrode. Can be prepared.

The electrode to be applied together with the separator containing the blowing agent of the present invention is not particularly limited, and the electrode active material may be prepared in a form bound to the electrode current collector according to conventional methods known in the art.

The positive electrode active material may be a conventional positive electrode active material that can be used for the positive electrode of the conventional electrochemical device, non-limiting examples thereof, such as LiM _x O _y (M = Co, Ni, Mn, Co _a Ni _b Mn _c ) Lithium transition metal composite oxides (for example, lithium manganese composite oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO ₂ , lithium cobalt oxides such as LiCoO ₂ , and some of manganese, nickel, and cobalt oxides thereof Or a vanadium oxide containing lithium or the like, or a chalcogen compound (for example, manganese dioxide, titanium disulfide, molybdenum disulfide, or the like). Preferably LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi _1-Y Co _Y O ₂ , LiCo _1-Y Mn _Y O ₂ , LiNi _1-Y Mn _Y O ₂ (where 0 ≦ Y <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _2-z Ni _z O ₄ , LiMn _2-z Co _z O ₄ ( Here, 0 <Z <2), LiCoPO ₄ , LiFePO _4, or a mixture thereof is mentioned. More preferably, it is a lithium transition metal composite oxide represented by the following formula (2).

Li _x MO ₂

Wherein M is Ni, Co, or Mn, and x is 0.05 ≦ x ≦ 1.10.

The negative electrode active material may be a conventional negative electrode active material that can be used for the negative electrode of the conventional electrochemical device, non-limiting examples of lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, Lithium adsorbents such as graphite or other carbons. Non-limiting examples of the positive electrode current collector is a foil made by aluminum, nickel or a combination thereof, and non-limiting examples of the negative electrode current collector by copper, gold, nickel or copper alloy or a combination thereof Foils produced.

Conventional binders may be used, and non-limiting examples thereof include polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), teflon, or mixtures thereof.

The conductive agent is not particularly limited as long as it can improve conductivity, and non-limiting examples thereof include acetylene black or graphite.

Using the electrolyte salts is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, and B ^- is PF ₆ ^-, BF _{^{4 -, Cl -, Br -}} , I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2) 3 ^- is a salt containing an anion ion or a combination thereof, such as. In particular, a lithium salt is preferable.

Organic solvents may be used conventional solvents known in the art, such as cyclic carbonates and / or linear carbonates, non-limiting examples of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl Carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC) Gamma butyrolactone (GBL), fluoroethylene carbonate (FEC), methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, ethyl propionate, butyl propionate or these And mixtures thereof. Moreover, the halogen derivative of the said organic solvent can be used, and it can also be used for the battery using water.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and the required physical properties of the final product. That is, it may be applied before the battery assembly or at the end of battery assembly.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

[Examples 1 to 3]

Example 1

1-1. Manufacturing membrane coated with blowing agent

5 parts by weight of Azobis (2-cyanobutane), a blowing agent, was added to 95 parts by weight of PVDF binder, and dispersed in a mixer for 1 hour. The prepared coating solution was coated on the polyethylene separator surface by the impregnation method with a weight of 10 mg / cm 2 and then dried by hot air at 110 to 120 ° C.

1-2. Battery manufacturing

(Cathode production)

Carbon powder as a negative electrode active material, polyvinylidene fluoride (PVDF) as a binder, and a conductive agent were mixed in a weight ratio of 91: 4: 5, and then dispersed in NMP to prepare a negative electrode mixture slurry. This negative electrode mixture slurry was uniformly applied to a cross section of a Cu foil having a thickness of 10 μm with a negative electrode current collector with a comma gap of 200 μm and then dried. The coating speed at this time was 3 m / min. Stability was measured by sampling the dried electrode, the results of which are shown in Table 1 below.

(Anode manufacturing)

A positive electrode mixture slurry was prepared by mixing a lithium cobalt composite oxide as a cathode active material, carbon as a conductive agent, and PVDF as a binder in a weight ratio of 95: 2.5: 2.5, and then adding it to NMP as a solvent. The positive electrode mixture slurry was applied to an Al thin film of a positive electrode current collector having a thickness of 20 μm, and coated and dried in the same manner as the negative electrode.

 (Battery manufacturing)

As a separator, a porous polyethylene film coated with a foaming agent was used in Example 1-1, and a jelly roll was manufactured by laminating a band-shaped cathode and an anode and winding it several times. The length and width were adjusted so that it was properly embedded in a battery can having an outer diameter of 18 mm and a height of 65 mm. The manufactured jelly roll was accommodated in the battery can, and the insulating plates were disposed on both upper and lower surfaces of the electrode element. Then, a negative electrode lead made of nickel was drawn from the current collector and welded to the battery can, and a positive electrode lead made of aluminum was drawn from the positive electrode current collector, and welded to an aluminum pressure release valve mounted on the battery cover to manufacture a battery. An electrolyte was injected into the prepared battery, and LiPF ₆ was used as a solvent and an electrolyte in which EC and EMC were mixed in a volume ratio of 1: 2.

The battery prepared as described above was charged to 4.2V with a constant current. The standard capacity of the electrolyte secondary battery was 2200 mAh, and the efficiency was measured at a rate of 1 C (2200 mA / h) and 0.2 C (440 mA / h) with constant current from 4.2 V to 3 V, and then the safety test of the battery was conducted. .

Example 2

Instead of using 95 parts by weight of PVDF and 5 parts by weight of blowing agent, the membrane was prepared by performing the same method as in Example 1 except that the PVDF was changed to 85 parts by weight and 15 parts by weight of blowing agent. Secondary batteries were prepared.

Example  3

Instead of using 95 parts by weight of PVDF and 5 parts by weight of blowing agent, the same method as in Example 1 was carried out except that the parts were changed to 75 parts by weight of PVDF and 25 parts by weight of blowing agent. Secondary batteries were prepared.

Comparative Example 1

A battery was manufactured in the same manner as in Example 1, except that a conventional polyethylene (PE) separator without a blowing agent was used.

Experimental Example 1. Evaluation of battery safety

In order to evaluate the safety of the lithium secondary battery having a separator coated with a blowing agent according to the present invention, it was performed as follows.

The lithium secondary batteries prepared in Examples 1 to 3 were used, and the lithium secondary batteries of Comparative Example 1 prepared in accordance with conventional methods known in the art were used without using a blowing agent as a control.

1-1. Hot box experiment

Each cell was stored for 4 hours at a high temperature of 160 ° C., respectively, after which the state of the cell is shown in Table 1 below.

As a result of the experiment, the lithium secondary battery of Comparative Example 1 having a separator prepared according to a conventional method without using a foaming agent caused a decrease in safety of the battery by about 60%, while the batteries of Examples 1 to 3 containing a foaming agent. Showed an excellent safety improvement effect (see Table 1).

1-2. Overcharge Experiment

Each battery was charged under the condition of 12V / 1C, and then the state of the battery is shown in Table 1 below.

Similar to the hot box test results, the battery of Examples 1 to 3 containing the blowing agent has an excellent safety improvement effect compared to the lithium secondary battery of Comparative Example 1 having an electrode prepared according to a conventional method without using a blowing agent. It was confirmed that the (see Table 1).

1-3. Penetration Experiment

Nail penetration test was performed using each cell, and then the state of the cell is described in Table 1 below.

Similar to the results of the hot box test and the overcharge test, the batteries of Examples 1 to 3 containing the foaming agent have excellent safety compared to the lithium secondary battery of Comparative Example 1 having the electrode prepared according to a conventional method without using the foaming agent. It was confirmed again that the improvement effect was shown (refer Table 1).

The present invention can significantly improve the safety that has been pointed out as a problem of a conventional lithium secondary battery by using a blowing agent as a coating component of the separator.

Claims (17)

(a) a porous substrate having pores; And (b) a foaming agent-containing coating layer formed on the surface of the substrate or a part of the pores Separation membrane comprising a, wherein the blowing agent is characterized in that to discharge a gas other than oxygen at the internal temperature (T) of the battery 100 to 120 ℃ range. The separation membrane of claim 1, wherein the temperature (T) is higher than a normal operating temperature of the battery and lower than a temperature at which shrinkage of the porous substrate provided in the battery occurs. delete The separator of claim 1, wherein the gas is at least one inert gas selected from the group consisting of N ₂ , He, Ne, Ar, Kr, and Xe. According to claim 1, wherein the separator is characterized in that the contact with oxygen is blocked due to gas other than oxygen generated from the blowing agent in the internal temperature (T) of the battery range from 100 to 120 ℃. The separator according to claim 1, wherein the separator operates the vent through an increase in the internal pressure of the battery due to the gas generated from the blowing agent in the temperature T of the battery in the range of 100 to 120 ° C. According to claim 1, wherein the separator is characterized in that the membrane shrinkage through the temperature rise control is suppressed by the foaming agent absorbs and decomposes the heat in the battery in the internal temperature (T) of the battery 100 to 120 ℃ range. The electrode of claim 1, wherein the blowing agent is an azo (-N = N-)-based compound The separation membrane of claim 8, wherein the azo compound is a compound represented by Formula 1 below. [Formula 1]

The separator of claim 1, wherein the blowing agent-containing coating layer comprises a binder polymer. The separator according to claim 10, wherein the content of the blowing agent is 0.5 to 50 parts by weight based on 100 parts by weight of the binder polymer. The method of claim 1, wherein the porous substrate having the pores is polyethylene, polypropylene, polyethylene terephthalate (polyethyleneterephthalate), polybutylene terephthalate (polybutyleneterephthalate), polyester (polyester), polyacetal (polyacetal), polyamide ( polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfidro and polyethylenenaphthalene Separation membrane of at least one member selected from the group consisting of polyethylenenaphthalene). The separation membrane of claim 1, wherein the separation membrane is coated with a blowing agent in a range of 0.1 to 30 mg / cm ² . An electrochemical device comprising an anode, a cathode, a separator, and an electrolyte, wherein the separator is an separator of any one of claims 1 to 2 and 4 to 13. The electrochemical device of claim 14, wherein the electrochemical device is a lithium secondary battery. (a) adding a blowing agent and a binder polymer to a solvent or a dispersion medium to prepare a blowing agent-containing binder solution; And (b) coating the solution on the surface of the porous substrate having the pores or a part of the pores and then drying the solution The manufacturing method of the separation membrane in any one of Claims 1-2 and 4-13 containing. The method of claim 16, wherein the coating step (b) impregnates the blowing agent-containing binder solution with a porous substrate having pores or nozzle sprays the solution.