KR102062315B1 - Manufacturing method of closslinked polyolefine separator and separator manufactured by the same method - Google Patents

Abstract

Preparing a polyolefin solution grafted with a silane-hydroxyl group-containing inorganic material using a polyolefin, a diluent, an alkoxy-containing vinylsilane, a hydroxyl group-containing inorganic material, and an initiator; Molding a polyolefin solution grafted with the silane-hydroxy group-containing inorganic material into a sheet form; Extracting a diluent from the sheet to produce a porous membrane; And crosslinking the porous membrane in the presence of moisture.

Description

Manufacturing method of crosslinked polyolefin separator and separator manufactured by the same {Manufacturing METHOD OF CLOSSLINKED POLYOLEFINE SEPARATOR AND SEPARATOR MANUFACTURED BY THE SAME METHOD}

The present invention relates to a method for producing a crosslinked polyolefin separator and a separator prepared thereby, and more particularly, to a method for preparing a crosslinked polyolefin separator having improved heat resistance and electrolyte solution wettability, and a separator prepared thereby.

Secondary batteries are chemical batteries that can be used semi-permanently by repeatedly charging and discharging using an electrochemical reaction, and are classified into lead acid batteries, nickel cadmium batteries, nickel hydrogen batteries, and lithium secondary batteries. Of these, lithium secondary batteries are leading the secondary battery market with superior voltage and energy density characteristics compared to other batteries, and lithium ion batteries using liquid electrolytes and lithium ions using solid electrolytes, depending on the type of electrolyte. It is divided into polymer battery.

The lithium secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. Among them, the required characteristics of the lithium secondary battery separator are separated from the positive electrode and the negative electrode to electrically insulate the ions, thereby increasing the permeability of lithium ions based on high porosity. It is to increase the conductivity. As the polymer material of the separator, which is generally used, it is advantageous to form pores, and polyolefins such as polyethylene, which are excellent in chemical resistance, mechanical properties, and electrical insulation properties, and which are inexpensive, are mainly used.

However, when the melting point of polyethylene is about 130 ° C., the heat generation of the battery does not have dimensional stability at a high temperature above the melting point, and shrinkage deformation occurs. In this case, the anode and the cathode meet to cause internal short circuit and thermal runaway, leading to ignition.

In order to improve such low thermal properties, methods of improving the heat shrinkage at high temperature by coating an inorganic material or a heat resistant polymer on the surface of polyethylene have been developed, and one of them is crosslinking silane-grafted polyethylene. .

However, silane-grafted polyethylene is relatively hydrophobic compared to polyethylene and has a problem of poor wettability with an electrolyte that is hydrophilic, and technology development is still required.

The present invention, in order to solve the above problems, by using an inorganic material including a hydroxyl group, provides a method for producing a cross-linked polyolefin separation membrane with improved hydrophilicity and the separation membrane produced thereby.

Other objects and advantages of the invention will be understood by the following description. In addition, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means or method described in the claims and combinations thereof.

The present invention, in order to solve the above problems, by using an inorganic material including a hydroxyl group, provides a method for producing a cross-linked polyolefin separation membrane with improved hydrophilicity and the separation membrane produced thereby.

Other objects and advantages of the invention will be understood by the following description. In addition, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means or method described in the claims and combinations thereof.

In order to solve the above problems, according to an aspect of the present invention, preparing an inorganic bond silane-grafted polyolefin solution using a polyolefin, a diluent, an alkoxy-containing vinyl silane, a hydroxyl group-containing inorganic material, and an initiator, the inorganic bond silane A method for producing a crosslinked polyolefin separation membrane is provided, which comprises forming a grafted polyolefin solution into a sheet form, extracting a diluent from the sheet, preparing a porous membrane, and crosslinking the porous membrane in the presence of water.

The preparing of the inorganic-bonded silane-grafted polyolefin solution may include mixing polyolefin, a diluent, an alkoxy-containing vinyl silane, a hydroxyl-containing inorganic material, and an initiator by injecting the extruder into a mixture, followed by reaction extrusion.

The diluent content may be 30 to 60 parts by weight, and the hydroxyl group-containing inorganic material may be 20 to 30 parts by weight based on 100 parts by weight of the polyolefin in the inorganic bonded silane-grafted polyolefin solution.

The polyolefin is polyethylene; Polypropylene; Polybutylene; Polypentene: polyhexene: polyoctene: at least one copolymer of ethylene, propylene, butene, pentene, 4-methylpentene, hexene, octene; Or mixtures thereof.

The diluent may be 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 it may include one or more selected from the group consisting of fatty acid esters.

The hydroxyl group-containing inorganic material may include one or more selected from the group consisting of aluminum hydroxide, magnesium hydroxide and bomite.

Forming into the sheet may include extruding the inorganic bonded silane-grafted polyolefin solution through a die to form an extrudate; Cooling the extrudate to form a cooled extrudate; And biaxially stretching the cooled extrudate in the longitudinal and transverse directions to form a stretched sheet.

The crosslinking may be carried out at 50 to 100 ° C. and 50 to 100% humidity of the porous membrane.

In addition, in order to achieve the above object, according to another aspect of the present invention there is provided a crosslinked polyolefin separation membrane prepared by the above-described manufacturing method.

The crosslinked polyolefin separator may have a crosslinking degree of 10% or more.

The crosslinked polyolefin separator may have a melt down temperature of 150 ° C. or higher.

In addition, according to another aspect of the present invention, there is provided a lithium secondary battery including the crosslinked polyolefin separator described above.

The present invention includes an inorganic material, while maintaining the melt down temperature while maintaining the shape of the separator has the advantage of minimizing the shrinkage.

In addition, the present invention has the advantage of improving the impregnation of the electrolyte due to the addition of the hydrophilic inorganic material.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings appended hereto illustrate preferred embodiments of the present invention, and together with the teachings of the present invention serve to better understand the technical idea of the present invention, the present invention is limited only to those described in such drawings. It is not to be interpreted.
1 is a flow chart of a crosslinked polyolefin membrane production method according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors should properly define the concept of terms in order to explain their invention in the best way. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that it can. Therefore, the embodiments shown in the specification and the configuration shown in the drawings are only the most preferred embodiment of the present invention, and do not represent all of the technical idea of the present invention, it is possible to replace them at the time of the present application It should be understood that there may be various equivalents and variations in the range.

1 is a flow chart of a method for producing a crosslinked polyolefin separator according to an embodiment of the present invention. Referring to Figure 1, the method for producing a crosslinked polyolefin membrane of the present invention is a step of preparing an inorganic grafted polyolefin solution (S100), the step of forming into a sheet (S200), a porous membrane manufacturing step (S300), and crosslinking Step S400 is included.

The inorganic grafted polyolefin solution manufacturing step (S100) is a step of preparing an inorganic-bonded silane-grafted polyolefin solution using a polyolefin, a diluent, an alkoxy-containing vinyl silane, a hydroxyl group-containing inorganic material and an initiator.

Specifically, the polyolefin, the diluent, the alkoxy-containing vinylsilane, the hydroxyl-containing inorganic material, and the initiator may be added to the extruder, mixed, and then subjected to reaction extrusion.

Examples of the polyolefin include polyethylene; Polypropylene; Polybutylene; Polypentene: polyhexene: polyoctene: at least one copolymer of ethylene, propylene, butene, pentene, 4-methylpentene, hexene, octene; Or mixtures thereof may be used.

Particularly, the polyethylene includes low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), and the like. Among them, high density polyethylene having high crystallinity and high melting point of resin is most preferred.

The molecular weight of the polyolefin is not important as long as it can be molded into a sheet shape. However, in the case where a strong physical property is required, such as a separator for a secondary battery, a higher molecular weight is better. In this case, the weight average molecular weight of the preferred polyolefin is 1 × 10 ⁵ to 3 × ^{10 6} , more preferably 3 × ^{10 5} to 1 × 10 ⁶ . As the diluent, liquid or solid paraffin oil, mineral oil, wax, soybean oil, etc. which are generally used for preparing a wet separator may be used.

In addition, a diluent capable of separating liquid-liquid phase with a polyolefin may be used as the diluent, and examples thereof include dibutyl phthalate, dihexyl phthalate, and dioctyl phthalate. Phthalic acid esters of; Aromatic ethers such as diphenyl ether and benzyl ether; Fatty acids having 10 to 20 carbon atoms, such as palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid; Fatty acid alcohols having 10 to 20 carbon atoms such as palmitic alcohol, stearic acid alcohol, and oleate alcohol; Mono-, di-, or triesters, palmitic acid mono-, di-, or triesters. One double-substituted saturated or unsaturated fatty acid or unsaturated fatty acid having 4 to 26 carbon atoms of a fatty acid group such as mono-oleic acid, mono-, di- or triester, linoleic acid mono-, di- or triester substituted with epoxy Or fatty acid esters in which two or more fatty acids have 1 to 8 hydroxyl groups and are ester-bonded with alcohols having 1 to 10 carbon atoms.

In addition, the diluent may be used as a mixture containing two or more of the aforementioned components.

Non-limiting examples of the alkoxy-containing vinyl silane may be used alone or in a mixture of two or more of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriethoxysilane, and the like. Such an alkoxy group-containing vinyl silane is grafted to the polyolefin by the vinyl group, the crosslinking reaction proceeds by the alkoxy group, and serves to crosslink the polyolefin.

In addition, the hydroxyl group-containing inorganic material that can be applied to the present invention may be one or more selected from the group consisting of aluminum hydroxide, magnesium hydroxide, boehmite.

Conventionally, in the case of a polyolefin separator in which only alkoxy-containing vinyl silane is grafted, there is a problem in that hydrophobic electrolyte and wettability are relatively poor compared to polyolefin itself, and the present invention includes a hydroxyl group-containing inorganic material to solve such a problem. Wetness with electrolyte solution was improved.

Formula 1 represents the reaction of an aluminum hydroxide-bonded silane-grafted polyolefin using aluminum hydroxide according to one embodiment of the present invention.

<Formula 1>

With respect to 100 parts by weight of the polyolefin in the inorganic bonded silane grafted polyolefin solution, the content of the diluent is 30 to 60 parts by weight, preferably 40 to 50 parts by weight, if the content of the diluent exceeds the stated weight If the viscosity is too low, there is a problem that T-die can flow down without passing through the casting roll during the extrusion process. On the contrary, if it does not reach the stated weight, the viscosity is high and the pressure in the extruder increases, and the desired pore size and porosity. I don't have it

In addition, the content of the hydroxyl group-containing inorganic material is 20 to 30 parts by weight, preferably 23 to 27 parts by weight based on 100 parts by weight of the polyolefin in the inorganic bond silane-grafted polyolefin solution. If the inorganic content is more than 30, the inorganic desorption and film forming uniformity is inferior and less than 20, the thermal safety effect is insufficient.

Forming 200 into a sheet may include extruding the inorganic bonded silane-grafted polyolefin solution through a die to form an extrudate; Cooling the extrudate to form a cooled extrudate; And biaxially stretching the cooled extrudate in the longitudinal and transverse directions to form the stretched sheet.

That is, the inorganic-bonded silane-grafted polyolefin solution obtained through the reaction extrusion is extruded using an extruder equipped with a teeth or the like, and then cold-extruded using a general casting or calendering method using water cooling and air cooling. It can form water.

Thereafter, the sheet is stretched using the cold extrudate to form a sheet, and as a result, it is possible to impart the improved strength required for the secondary battery separator.

This stretching can be carried out in a roll system or tenter type shaft or simultaneous stretching. The draw ratio is three times or more, preferably 5 to 10 times in the longitudinal and transverse directions, respectively, and the total draw ratio is preferably 20 to 80. If the draw ratio in one direction is less than three times, the orientation in one direction is not sufficient, and at the same time, the balance of physical properties between the longitudinal direction and the transverse direction may be broken, thereby lowering tensile strength and puncture strength. In addition, the total draw ratio is less than 20 times and unstretched, pore formation may not be made, if more than 80 times breakage occurs during stretching, there may be a disadvantage that the shrinkage of the final film is increased.

In this case, the stretching temperature may vary depending on the melting point of the polyolefin used and the concentration and type of the diluent. Preferably, the stretching temperature is selected from a temperature range in which 30 to 80% by weight of the crystal part of the polyolefin in the sheet is melted. It is suitable. If the stretching temperature is selected in the temperature range lower than the melting temperature of 30% by weight of the crystalline portion of the polyolefin in the sheet molding, there is no softness of the film, the stretchability is worse, the breakage is likely to occur during stretching and unburned God also happens. On the other hand, when the stretching temperature is selected in the temperature range higher than the melting temperature of 80% by weight of the crystal portion, the stretching is easy and less unstretched, but the thickness deviation occurs due to partial overstretching, the orientation effect of the resin is less This will greatly fall. On the other hand, the degree of melting of the crystal portion with temperature can be obtained from differential scanning calorimeter (DSC) analysis of the film molding.

Porous membrane manufacturing step (S300) is a step of producing a porous membrane by extracting a diluent from the sheet.

Specifically, the diluent in the sheet is extracted and dried using an organic solvent, and the usable organic solvent is not particularly limited, and any solvent capable of extracting the diluent used for resin extrusion may be used. For example, as the organic solvent, methyl ethyl ketone, methylene chloride, hexane and the like having high extraction efficiency and fast drying are suitable.

As the extraction method, all general solvent extraction methods such as an immersion method, a solvent spray method, and an ultrasonic method may be used individually or in combination. The content of residual diluent at the time of extraction should preferably be 1% by weight or less. If the residual diluent exceeds 1% by weight, the physical properties decrease and the permeability of the porous membrane decreases. The amount of residual diluent may be influenced by the extraction temperature and extraction time, and the extraction temperature is preferably high in order to increase the solubility of the diluent and the organic solvent, but the temperature is preferably 40 ° C. or lower in consideration of the safety problem due to the boiling of the organic solvent. . If the extraction temperature is below the freezing point of the diluent, the extraction efficiency is greatly reduced, so it must be higher than the freezing point of the diluent.

In addition, the extraction time depends on the thickness of the porous membrane to be produced, but in the case of a porous membrane of 10 to 30㎛ thickness, 2 to 4 minutes is suitable.

Crosslinking step (S400) is a step of crosslinking the porous membrane in the presence of moisture. Specifically, the step of crosslinking is placed in a constant temperature and humidity chamber of 50 to 100 ° C., more preferably 60 to 90 ° C., and a humidity of 50 to 100%, more preferably 70 to 100%, or soaked in high temperature or boiling water. It can be allowed to proceed for several hours or days.

When the temperature and humidity at the time of crosslinking satisfy this range, the crosslinking rate can be increased, and the problem of deformation of the film due to melting of some polyethylene crystals at high temperature can be prevented.

In order to promote the crosslinking reaction, a crosslinking catalyst may be used. In general, as the crosslinking catalyst, carboxylate salts, organic bases, inorganic acids and organic acids of metals such as tin, zinc, iron, lead, and cobalt may be used. Specifically, dibutyl tin dilaurate, dibutyl tin diacetate, stannous acetate, first tin caprylate, lead naphthenate, zinc caprylate, cobalt naphthenate, ethylamine, dibutyl amine, hexyl Inorganic acids such as amine, pyridine, sulfuric acid, hydrochloric acid, organic acids such as toluenesulfonic acid, acetic acid, stearic acid and maleic acid.

As a method of using the crosslinking catalyst, there is a method of adding a crosslinking catalyst in the preparation of a silane-grafted polyethylene solution, a method of applying a solution or dispersion of the crosslinking catalyst to a porous membrane, and the like.

When the catalyst is added during the preparation of the silane grafted polyethylene solution, the content of the crosslinking catalyst is in the range of 0.0001 to 5% by weight relative to the silane grafted polyethylene solution. In addition, when the crosslinking catalyst is applied to the porous membrane, the concentration of the crosslinking catalyst may be adjusted in the range of 0.001 to 30% by weight based on the solution or dispersion of the crosslinking catalyst.

According to another aspect of the present invention there is provided a crosslinked polyolefin separator prepared by the above-described manufacturing method.

The crosslinked polyolefin separator according to one embodiment of the present invention has a crosslinking degree of 10% or more, preferably 20 to 80%, more preferably 30 to 80%.

In addition, the crosslinked polyolefin separator has a meltdown temperature of 150 ° C or higher, preferably 160 to 220 ° C, more preferably 170 to 200 ° C.

According to another aspect of the present invention, there is provided a lithium secondary battery comprising the crosslinked polyolefin separator described above.

The lithium secondary battery includes a cathode, an anode, and a crosslinked polyolefin separator according to one aspect of the present invention.

These cathodes and anodes can be prepared in the form of the electrode active material bound to the electrode current collector according to conventional methods known in the art. Non-limiting examples of the cathode active material of the electrode active material may be a conventional cathode active material that can be used in the cathode of the conventional electrochemical device, in particular lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide or a combination thereof One lithium composite oxide can be used. Non-limiting examples of anode active materials include conventional anode active materials that can be used for the anodes of conventional electrochemical devices, in particular lithium metal or lithium alloys, carbon, petroleum coke ), Lithium adsorbents such as activated carbon, graphite or other carbons can be used. Non-limiting examples of cathode current collectors include foils made of aluminum, nickel, or combinations thereof, and non-limiting examples of anode current collectors include copper, gold, nickel, or copper alloys or combinations thereof. Foils produced.

In addition, the electrolyte that may be used in the lithium secondary battery according to an aspect of the invention, A ⁺ B ^- A salt of the structure, such as, A ⁺ is an alkali metal cation or a combination of these, 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 - salts comprising the anions or an ion composed of a combination of propylene carbonate (PC like), ethylene carbonate (EC), diethyl carbonyl net (DEC), dimethyl Carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC) , Dissolved or dissociated in an organic solvent consisting of gamma butyrolactone (g-butyrolactone) or mixtures thereof, but not limited thereto. It is not.

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.

As a process of applying the crosslinked polyolefin separation membrane according to an aspect of the present invention as a secondary battery, a lamination (stacking) and folding process of a separator and an electrode may be performed in addition to the general winding process.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example 1

The resin used for the coating was high density polyethylene, with a weight average molecular weight of 300,000 and a melting temperature of 135 degrees. The diluent used was liquid paraffin oil with a kinematic viscosity of 40 cSt at 40 degrees. Aluminum hydroxide used as an inorganic material has a D50 of 1.3 μm and a BET of 3.5 m 2 / g. The ratios of high density polyethylene, diluent and inorganic components were 25wt%, 50wt% and 25wt%, respectively. Trimethoxy vinyl silane was used as the vinyl silane and the content was 2 phr relative to the total content. The initiator was 2 / 5-dimethyl-2,5-di (tert-butylperoxy) hexane as 1/50 of vinylsilane. The above components were put into a twin screw extruder and kneaded to make a polyethylene solution, and at the same time, the reaction extrusion was performed to graf the aluminum hydroxide bonded silane to polyethylene. After the die and the cold casting rolls, the sheet was formed, followed by MD stretching, followed by biaxial stretching using a tenter-type stretching machine of TD stretching. MD draw ratio and TD draw ratio were both 5.5 times. The stretching temperature was 108 degrees in MD and 123 degrees in TD. The stretched membrane was extracted with liquid paraffin with methylene chloride and heat-set at 126 degrees to prepare a porous membrane. The obtained porous membrane was placed in an incubation chamber at 80 degrees and 90% humidity for 24 hours for crosslinking to prepare a crosslinked polyolefin separation membrane.

Comparative Example 1

The resin used for the coating was high density polyethylene with a weight average molecular weight of 300,000 and a melting temperature of 135 degrees. The diluent used was liquid paraffin oil with a kinematic viscosity of 40 cSt at 40 degrees. The ratio of the two components is 35wt% and 65wt%. The vinylsilane was trimethoxyvinylsilane and the content was 2phr compared to the resin and diluent combination. The initiator was 2 / 5-dimethyl-2,5-di (tert-butylperoxy) hexane as 1/50 of vinylsilane. The above components were put into a twin screw extruder and kneaded to make a polyethylene solution, and at the same time, the reaction was extruded and silane was grafted to polyethylene. After the die and the cold casting rolls, the sheet was formed, followed by MD stretching, followed by biaxial stretching using a tenter-type stretching machine of TD stretching. MD draw ratio and TD draw ratio were both 5.5 times. The stretching temperature was 108 degrees in MD and 123 degrees in TD. The stretched membrane was extracted with liquid paraffin with methylene chloride and heat-set at 126 degrees to prepare a porous membrane. The obtained porous membrane was placed in an incubation chamber at 80 ° C. and 90% humidity for 24 hours to crosslink to prepare a membrane.

The thickness, aeration time, heat shrinkage, and contact angle of the separators prepared in Example 1 and Comparative Example 1 were measured, respectively, and the results are shown in Table 1 below.

Condition Example 1 Comparative Example 1 thickness Μm 14.9 14.6 Aeration time Sec / 100cc 298 405 Heat shrinkage
(150 ℃ / hr) MD % 57.4 54.8 TD 39.2 44.2 Contact angle
(contact angle) ° 26.5 33.4

The thermal shrinkage is measured by MD / TD shrinkage after 1 hour in 150 ℃ oven (oven).

 ※ shrinkage of heat; %) = [(L0-L) / L0] x 100 where L0 is the initial specimen length and L is the specimen length after heat treatment.

The contact angle was dropped one drop of electrolyte (LiPF ₆ 1mol, EC 1 / EMC 2 (vol%)) on the surface of the separator and after 30 seconds the contact angle of the electrolyte droplet to the surface of the separator was measured.

The aeration time and the electrolyte wetting (wetting) Improvement by introducing an inorganic material composite separator was developed more advantageous to the cell (Cell) performance.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto, and the technical concept and the following description of the present invention will be made by those skilled in the art to which the present invention pertains. Various modifications and variations are possible within the scope of equivalents of the claims to be described.

Claims (12)

Preparing a polyolefin solution in which a polyolefin, a diluent, an alkoxy-containing vinyl silane, a hydroxyl group-containing inorganic material, and an initiator are mixed in an extruder, followed by reaction extrusion to graf the silane-hydroxyl group-containing inorganic material;
Molding a polyolefin solution grafted with the silane-hydroxy group-containing inorganic material into a sheet form;
Extracting a diluent from the sheet to produce a porous membrane; And
Crosslinking the porous membrane in the presence of moisture;
The hydroxyl group-containing inorganic material is 20 to 30 parts by weight based on 100 parts by weight of the polyolefin solution,
Method for producing a crosslinked polyolefin separator, characterized in that the crosslinking degree is 30 to 80%.
delete The method of claim 1,
A method for producing a cross-linked polyolefin separator, characterized in that the diluent content is 30 to 60 parts by weight based on 100 parts by weight of the polyolefin solution in the polyolefin solution grafted with the silane-hydroxy group-containing inorganic material. The method of claim 1,
The polyolefin is polyethylene; Polypropylene; Polybutylene; Polypentene: polyhexene: polyoctene: at least one copolymer of ethylene, propylene, butene, pentene, 4-methylpentene, hexene, octene; Or a method for producing a cross-linked polyolefin separation membrane comprising a mixture thereof. The method of claim 1,
The diluent is 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, the method for producing a crosslinked polyolefin separation membrane comprising at least one member selected from the group consisting of The method of claim 1,
The hydroxyl group-containing inorganic material is a method for producing a cross-linked polyolefin separator, characterized in that it comprises one or more selected from the group consisting of aluminum hydroxide, magnesium hydroxide, boehmite. The method of claim 1,
Forming the sheet may include extruding a polyolefin solution grafted with the silane-hydroxyl group-containing inorganic material through a die to form an extrudate; Cooling the extrudate to form a cooled extrudate; And biaxially stretching the cooled extrudate in the longitudinal and transverse directions to form a sheet to form a cross-linked polyolefin separator. The method of claim 1,
The step of crosslinking is a method for producing a crosslinked polyolefin separator, characterized in that the porous membrane is carried out at a temperature of 50 to 100 ℃ and humidity conditions of 50 to 100%. A crosslinked polyolefin separator prepared by the method according to any one of claims 1 and 3 to 8. The method of claim 9,
The crosslinked polyolefin separator has a crosslinking degree of 30% to 80%. The method of claim 9,
The crosslinked polyolefin separator has a melt down temperature of 150 ° C. or higher. A lithium secondary battery comprising the crosslinked polyolefin separator of claim 9.

Images