KR20160129574A - Polyolefin separator and the method of preparing the same - Google Patents

Abstract

The present invention is to provide a polyolefin separator which can reduce the thickness and the weight compared to a conventional composite separator having organic/inorganic coating layers, and has a heat radiation property equivalent to that of the conventional composite separator. The separator for an electrochemical device comprises: a porous polymer film; and a porous coating layer including an epoxy resin curing material, and formed in one surface or both surfaces of the porous polymer film.

Description

Polyolefin separator and method of manufacturing same

The present invention relates to a polyolefin separator having excellent economical efficiency and heat resistance and a method for producing the same.

A secondary battery is a chemical battery that can be used semi-permanently by repeatedly charging and discharging by electrochemical reaction, and is classified into a lead acid battery, a nickel cadmium battery, a nickel hydrogen battery, and a lithium secondary battery. The lithium secondary battery is superior to other batteries in terms of high voltage and energy density characteristics, leading the secondary battery market. Depending on the type of electrolyte, a lithium ion battery using a liquid electrolyte and a lithium ion battery using a solid electrolyte Polymer battery.

The lithium secondary battery is composed of a cathode, an anode, an electrolytic solution and a separator. The lithium secondary battery separator is required to separate the anode and the cathode from each other and electrically insulate it from each other while enhancing the permeability of lithium ions based on the high porosity. . Polyolefins such as polyethylene, which are advantageous for pore formation and have excellent chemical resistance, mechanical properties, electrical insulation characteristics, and low cost, are mainly used as polymer materials of membranes which are generally used.

However, when the melting point of polyethylene is as low as about 130 ° C, heat generation of the battery causes shrinkage deformation without having dimensional stability at a temperature higher than the melting point. In this case, the anode and the cathode meet and cause an internal short circuit and thermal runaway phenomenon, which leads to ignition.

In order to improve such low thermal properties, methods of improving heat shrinkage at high temperature have been developed by using a method of coating inorganic or heat-resistant polymer on the surface of polyethylene.

However, such a coating improves the safety, but increases the packing density and increases the weight of the battery.

Therefore, separation membranes are still required to maintain the heat resistance while reducing the thickness and weight of the composite separator.

Accordingly, a problem to be solved by the present invention is to provide a polyolefin separator having excellent heat resistance, even if its thickness and weight are reduced, and a method for producing the same.

According to an aspect of the present invention, there is provided a porous polymer film comprising: a porous polymer film; And a porous coating layer formed on one surface or both surfaces of the porous polymer film including a cured product of an epoxy resin.

Preferably, the epoxy resin may be at least one selected from the group consisting of an aromatic epoxy resin and a non-aromatic epoxy resin.

Wherein the aromatic epoxy resin is selected from the group consisting of bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, fluorene containing epoxy resin and triglycidyl isocyanurate It may be more than one kind.

Wherein the non-aromatic epoxy resin is selected from the group consisting of an aliphatic glycidyl ether type epoxy resin, an aliphatic glycidyl ester type epoxy resin, an alicyclic glycidyl ether type epoxy resin and an alicyclic glycidyl ester type epoxy resin It can be more than a species.

Preferably, the cured product of the epoxy resin may be a cured product of a curing composition comprising an epoxy resin, a curing agent and an organic solvent.

Preferably, the curing agent may be at least one of an aromatic curing agent and a non-aromatic curing agent.

Preferably, the organic solvent may be polar organic daily.

Preferably, the porous polymer film may be a porous polyolefin film. Wherein the porous polyolefin film comprises polyethylene; Polypropylene; Polybutylene; Polypentene: polyhexene: polyolefin: at least one copolymer of ethylene, propylene, butene, pentene, 4-methylpentene, hexene, and octene, or a mixture thereof.

Preferably, the porous polymer film may have a thickness of 5 to 50 탆, and the porous coating layer may have a thickness of 0.01 to 1 탆.

According to another aspect of the present invention, there is provided an electrochemical device including a cathode, an anode, and the above-described separator interposed between the cathode and the anode.

Preferably, the electrochemical device may be a lithium secondary battery.

According to another aspect of the present invention, there is also provided a method of manufacturing a porous polyolefin film, comprising: preparing a porous polyolefin film; Coating at least one surface of the porous polyolefin film with a composition for forming a porous coating layer comprising an epoxy resin, a curing agent and an organic solvent; And curing the porous polyolefin film coated with the composition to obtain a composite separator having a porous coating layer formed thereon.

Preferably, the curing can be carried out at a temperature of 70 to 100 DEG C for 5 to 20 hours.

Preferably, the porous polyolefin film is selected from the group consisting of polyethylene; Polypropylene; Polybutylene; Polypentene: polyhexene: polyolefin: at least one copolymer of ethylene, propylene, butene, pentene, 4-methylpentene, hexene, and octene, or a mixture thereof.

Preferably, the plasticizer is selected from the group consisting of paraffin oil, mineral oil, wax, soybean oil, phthalic acid esters, aromatic ethers, fatty acids having 10 to 20 carbon atoms; Fatty acid alcohols having 10 to 20 carbon atoms; And fatty acid esters.

According to the present invention, it is possible to provide a polyolefin separator which can reduce the thickness and weight of a conventional composite separator having an organic / inorganic coating layer and has an equivalent heat resistance.

Further, according to the present invention, it is possible to provide a polyolefin separator having improved chemical resistance, electric insulation of high voltage, and water resistance compared to conventional separator and improved electrolyte wettability, and productivity is improved by not using conventional organic / inorganic coating slurry .

Hereinafter, the present invention will be described in detail with reference to the drawings. The 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 appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

According to one aspect of the present invention, a separation membrane for an electrochemical device includes: a porous polymer film; And a porous coating layer formed on one side or both sides of the porous polymer film including a cured product of an epoxy resin.

The cured product of the epoxy resin may be a cured product of a curing composition comprising an epoxy resin, a curing agent and an organic solvent.

The epoxy resin is added in an amount of 1 to 5% by weight based on the total weight of the curing composition, and one or more selected from the group consisting of an aromatic epoxy resin and a non-aromatic epoxy resin can be used.

Wherein the aromatic epoxy resin is selected from the group consisting of bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, fluorene containing epoxy resin and triglycidyl isocyanurate The non-aromatic epoxy resin may be at least one selected from the group consisting of an aliphatic glycidyl ether type epoxy resin, an aliphatic glycidyl ester type epoxy resin, an alicyclic glycidyl ether type epoxy resin and an alicyclic glycidyl ester type epoxy A resin, and a resin.

The curing agent is added in an amount of 0.1 to 3 wt% based on the total weight of the curing composition, and may be one or more of an aromatic curing agent and a non-aromatic curing agent.

The aromatic curing agent may be selected from aromatic amines (e.g., m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, benzyldimethylamine, dimethylaminomethylbenzene, etc.), aromatic acid anhydrides At least one member selected from the group consisting of phenol novolak resins, heterocyclic ring-containing amines (e.g., triazine-ring-containing amines), and the like can be used, The aromatic curing agent is selected from the group consisting of aliphatic amines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, bis (hexamethylene) triamine, 1,3,6-trisaminomethylhexyl Polyamine diamine, trimethyl hexamethylene diamine, polyether diamine, etc.), alicyclic amines (isophorone diamine, (5,5) undecane adducts with 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxaspire, bis (4-amino 3-methylcyclohexyl) methane, bis (4-aminocyclohexyl) methane, modified products thereof, etc.), aliphatic polyamide amines composed of polyamines and dimer acids have.

The organic solvent is added in an amount of 90 to 99% by weight based on the total weight of the curing composition, and may be polar organic solvent. Examples of the polar organic solvent include xylene, toluene, acetone, methanol, isopropyl alcohol, methyl ethyl ketone, and methyl isobutyl ketone.

 The porous polymer film may be a porous polyolefin film, and the porous polyolefin film may be polyethylene; Polypropylene; Polybutylene; Polypentene: polyhexene: polyolefin: at least one copolymer of ethylene, propylene, butene, pentene, 4-methylpentene, hexene, and octene, or a mixture thereof.

The thickness of the porous polymer film may be 5 to 50 탆, and the thickness of the porous coating layer may be 0.01 to 1 탆.

The present invention also provides an electrochemical device comprising a cathode, an anode, and the separator interposed between the cathode and the anode. Preferably, the electrochemical device may be a lithium secondary battery.

The cathode and the anode may be manufactured by binding an electrode active material to an electrode current collector according to a conventional method known in the art. Examples of the cathode active material include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof A lithium complex oxide may be used. As a non-limiting example of the anode active material, a conventional anode active material that can be used for an anode of an electrochemical device can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium adsorbing materials such as graphite or other carbon-based materials and the like can be used. Non-limiting examples of the cathode current collector include aluminum, nickel, or a combination thereof, and examples of the anode current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

The electrolyte used in the lithium secondary battery according to one aspect of the present invention is a salt having a structure such as A ⁺ B ^- , where A ⁺ is an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ including consisting of ions 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 - a salt containing an ion composed of such anions, or a combination thereof, and 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 (G-butyrolactone) or a mixture thereof. However, it is not limited thereto. It is not fixed.

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.

According to another aspect of the present invention, there is provided a method of manufacturing a separation membrane for an electrochemical device, comprising: preparing a porous polyolefin film; Coating at least one surface of the porous polyolefin film with a composition for forming a porous coating layer comprising an epoxy resin, a curing agent and an organic solvent; And curing the porous polyolefin film coated with the composition to obtain a composite separator having a porous coating layer formed thereon.

The curing may be carried out at a temperature of 70 to 100 DEG C for 5 to 20 hours.

Examples of the plasticizer include paraffin oil, mineral oil, wax, soybean oil, phthalic acid esters, aromatic ethers, fatty acids having 10 to 20 carbon atoms; Fatty acid alcohols having 10 to 20 carbon atoms; And fatty acid esters may be used.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the following 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 following embodiments. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Manufacturing example

The polyolefin is high-density polyethylene, and has a weight average molecular weight of 300,000 and a melting temperature of 135 占 폚. The diluent used was liquid paraffin oil and had a kinematic viscosity of 40 cSt at 40 ° C. The weight ratio of the high-density polyethylene and liquid paraffin oil was 35:65.

The above ingredients were put into a twin-screw extruder and kneaded to make a polyethylene solution and extruded at a temperature of 135 ° C. The stretching temperature was 108 占 폚 in the longitudinal direction and 123 占 폚 in the transverse direction, and the stretching ratio was 5.5 times in the longitudinal direction. Next, liquid paraffin, which is a plasticizer, was extracted at a rate of 2 m / min using methylene chloride as an extraction solvent, and then heat set at 128 DEG C to obtain a porous polyolefin film.

Example  One

An epoxy resin (product name: KSR177, Kukdo Chemical Co., Ltd.) / a curing agent (product name: G649, Kukdo Chemical Co., Ltd.) / acetone as a curing composition was mixed at a weight ratio of 1.33 / 0.67 / 98.0.

The porous polyolefin film was impregnated into the curing composition, and then left in a convection oven at 80 ° C for 12 hours to prepare a 14.0 μm thick separation membrane having porous coating layers on both sides.

Example  2

The composition for curing was prepared by mixing an epoxy resin (product name: YDPN-636, Kukdo Chemical Co., Ltd.), a curing agent (product name: M-xylene diamine, Kukdo Kagaku), a 2-methyl imidazole / acetone at 1.67 / 0.33 / 0.04 / Weight ratio.

The porous polyolefin film was impregnated with the curing composition, and then left in a convection oven at 80 캜 for 12 hours to prepare a 14.2 탆 thick separation membrane having a porous coating layer on both sides.

Example  3

An epoxy resin (product name: KDT-440, Kukdo Chemical Co., Ltd.) / a curing agent (product name: isophorone diamine, Kukdo Chemical Co., Ltd.) / acetone as a curing composition was mixed at a weight ratio of 1.67 / 0.33 / 98.0.

The porous polyolefin film was impregnated with the curing composition, and then left in a convection oven at 80 캜 for 12 hours to prepare a 14.2 탆 thick separation membrane having a porous coating layer on both sides.

Comparative Example

The slurry for forming the coating layer was prepared by mixing Al2O3 particles / Cyanoalcohol / PVDF-HFP / acetone as a curing composition with a weight ratio of 18.0 / 0.3 / 1.7 / 80.

The slurry for forming a coating layer was coated on both surfaces of the porous polyolefin film to prepare a separation membrane having a thickness of 22.3 탆 in which a porous coating layer was formed on both surfaces.

Next, the weight per unit area, the aeration time and the heat shrinkage ratio of each of the separators for electrochemical devices according to Examples 1 to 3 and Comparative Examples described above were measured, and the results are shown in Table 1 below.

(1) Measurement of ventilation time

The time (sec) taken for 100 ml of air to pass through the separator was measured at a constant pressure (0.05 MPa) using an air flow meter (manufacturer: Asahi Seiko, product name: EG01-55-1MR). A total of 3 points were measured for each point of left / middle / right of the sample, and the average was recorded.

(2) Heat shrinkage

The membrane sample (size: 50 mm x 50 mm) was stored at 120 ° C and 60 min using a convection oven and the length of the part where the shrinkage was most severely occurred at room temperature was measured using a steel ruler. The heat shrinkage ratio Respectively. A total of 3 points were measured for each 1 point of left / middle / right of the sample, and the average was recorded.

Heat shrinkage percentage (%) = [1- (length of shrinkage most severe portion) / (initial length)] X 100

division Example  One Example  2 Example  3 Comparative Example Coating thickness ㎛ 0.1 0.2 0.2 8.3 Weight per area g / m ² 7.6 7.5 7.6 20.1 Ventilation time Sec / 100cc <400 <400 <400 <400 Heat shrinkage (%)
(120 DEG C / 30 minutes) MD <3 <3 <3 <3 TD <3 <3 <3 <3 Heat shrinkage (%)
(150 DEG C / 30 minutes) MD <50 <55 <55 <60 TD <40 <55 <40 <50

As shown in Table 1, it can be seen that the separator of Examples 1 to 3 according to the present invention has significantly reduced thickness and weight as compared with the separator of Comparative Example, and has the same heat shrinkage rate and ventilation time. Accordingly, the separator according to the present invention can provide a separator having excellent heat resistance, chemical resistance, electrical insulation of high voltage, and high water resistance because it can significantly reduce the thickness, weight and volume of the conventional separator. can do.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It goes without saying that various modifications and variations are possible within the scope of equivalence of the scope.

Claims (16)

Porous polymer films; And
And a porous coating layer formed on one surface or both surfaces of the porous polymer film including a cured product of an epoxy resin. The method according to claim 1,
Wherein the epoxy resin is at least one selected from the group consisting of an aromatic epoxy resin and a non-aromatic epoxy resin. 3. The method of claim 2,
Wherein the aromatic epoxy resin is selected from the group consisting of bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, fluorene containing epoxy resin and triglycidyl isocyanurate Wherein at least one of the first electrode and the second electrode is made of a metal. 3. The method of claim 2,
Wherein the non-aromatic epoxy resin is selected from the group consisting of an aliphatic glycidyl ether type epoxy resin, an aliphatic glycidyl ester type epoxy resin, an alicyclic glycidyl ether type epoxy resin and an alicyclic glycidyl ester type epoxy resin Type or more. The method according to claim 1,
Wherein the cured product of the epoxy resin is a cured product of a curing composition comprising an epoxy resin, a curing agent and an organic solvent. 6. The method of claim 5,
Wherein the curing agent is at least one of an aromatic curing agent and a non-aromatic curing agent. 6. The method of claim 5,
Wherein the organic solvent is a polar organic solvent. The method according to claim 1,
Wherein the porous polymer film is a porous polyolefin film. 9. The method of claim 8,
Wherein the porous polyolefin film comprises polyethylene; Polypropylene; Polybutylene; A separator for an electrochemical device, comprising polyphenylene: polyhexene: polyolefin: at least one copolymer selected from the group consisting of ethylene, propylene, butene, pentene, 4-methylpentene, hexene and octene; The method according to claim 1,
Wherein the thickness of the porous polymer film is in the range of 5 to 50 占 퐉 and the thickness of the porous coating layer is in the range of 0.01 to 1 占 퐉. An electrochemical device comprising a cathode, an anode, and a separator interposed between the cathode and the anode,
The electrochemical device according to any one of claims 1 to 10, wherein the separator is a separator for an electrochemical device. 12. The method of claim 11,
Wherein the electrochemical device is a lithium secondary battery. Preparing a porous polyolefin film;
Coating at least one surface of the porous polyolefin film with a composition for forming a porous coating layer comprising an epoxy resin, a curing agent and an organic solvent; And
And curing the porous polyolefin film coated with the composition to obtain a composite separator having a porous coating layer formed thereon. 14. The method of claim 13,
Wherein the curing is performed at a temperature of 70 to 100 DEG C for 5 to 20 hours. 14. The method of claim 13,
Wherein the porous polyolefin film comprises polyethylene; Polypropylene; Polybutylene; A process for producing a separator for electrochemical devices, which comprises: a polyphenylene: polyhexene: polyolefin: at least one copolymer selected from the group consisting of ethylene, propylene, butene, pentene, 4-methylpentene, hexene and octene; Way. 14. The method of claim 13,
Examples of the plasticizer include paraffin oil, mineral oil, wax, soybean oil, phthalic acid esters, aromatic ethers, fatty acids having 10 to 20 carbon atoms; Fatty acid alcohols having 10 to 20 carbon atoms; And at least one selected from the group consisting of aliphatic acid esters and fatty acid esters.