KR100926428B1 - Manufacturing method of multilayer polyolefin separator film for lithium secondary battery and multilayer polyolefin separator film therefrom - Google Patents

Abstract

The present invention relates to a method for manufacturing a multilayer polyolefin separator for a lithium secondary battery and a multilayer polyolefin separator for a lithium secondary battery manufactured therefrom. More specifically, the separator of the layer B / A / B has a high short-circuit temperature and a high temperature. The present invention relates to a method for preparing a multilayer polyolefin separator for a lithium secondary battery with improved membrane strength, and a multilayer polyolefin separator for a lithium secondary battery prepared therefrom. To this end, the method for preparing a multilayer polyolefin separator for a lithium secondary battery according to the present invention easily mixes a vinylidene fluoride-based polymer with a polyolefin using a compatibilizer, and a mixture thereof with polyolefin-vinyl together with liquid paraffin. Forming a layer A of a polymer form of lithium fluoride series, forming a layer B by kneading polypropylene and liquid paraffin, and forming the layer A and layer B into layers B / A / B. Coextrusion and casting, simultaneously biaxially stretching the cast sheet to prepare a separator, washing the biaxially stretched separator with a volatile solvent to remove liquid paraffin from the biaxially stretched separator, And heat-setting the washed biaxially stretched separator.

Polypropylene, compatibilizer, vinylidene fluoride, polyolefin, liquid paraffin, lithium secondary battery, separator, multicomponent system, microporous membrane

Description

MANUFACTURING METHOD OF MULTILAYER POLYOLEFIN SEPARATOR FILM FOR LITHIUM SECONDARY BATTERY AND MULTILAYER POLYOLEFIN SEPARATOR FILM THEREFROM}

The present invention relates to a method for manufacturing a multilayer polyolefin separator for a lithium secondary battery and a multilayer polyolefin separator for a lithium secondary battery manufactured therefrom. More specifically, the separator of the layer B / A / B has a high short-circuit temperature and a high temperature. The present invention relates to a method for preparing a multilayer polyolefin separator for a lithium secondary battery with improved membrane strength, and a multilayer polyolefin separator for a lithium secondary battery prepared therefrom.

Recently, as the use of mobile communication and portable electronic devices continues to increase and the rapid development of portable electronic devices, the demand for secondary batteries is gradually increasing. Light weight, miniaturization and high capacity are required.

In response to such demands, one of the most recent high-performance, next-generation advanced new batteries is a lithium secondary battery. Among them, lithium ion battery is excellent enough to occupy more than 60% of the world's secondary battery market, and its electrochemical performance is continuing, and many companies and research institutes The focus is on improving performance.

Meanwhile, the separator of the secondary battery is a 10-30 μm thick polymer membrane having a porous structure located between the positive electrode and the negative electrode, and not only provides a passage through which lithium ions can actively move, but also the positive electrode and the negative electrode. It serves to prevent contact. Recently, many kinds of materials are used as material separation membranes, but membranes manufactured using polyethylene are the mainstream.

In general, a separator of a lithium secondary battery has been used in various forms such as a polyolefin-based alone or a porous sheet or film made of polyolefin-based and ultra high molecular weight polyethylene.

Conventional technology related to the production of a separator that plays an important role in the performance and safety of such a lithium secondary battery is US Patent No. 6,413,676 (Lithium ion polymer electrolytes), in which the polyvinylidene fluoride is used The prepared membrane shows high ionic conductivity due to its good affinity with liquid electrolytes, while its mechanical properties are poor, and thus the separator is not commercialized as a separator for lithium secondary batteries requiring high mechanical properties in the manufacturing process. there was. In addition, the study on membranes prepared by coating PVdF on PE nonwoven fabrics (Novel porous separator based on PVdF and PE non-woven matrix for rechargeable lithium batteries, Journal of Power Sources, 139 (2005) 235-241) and PVdF only Korean Patent No. 0805760 and a paper (Preparation and characterization of new microporous stretched membrane for lithium rechargeable battery, Journal of Power Sources, 163 (2006) 247-251) have been published for the prepared separator.

On the other hand, currently commercialized polyethylene membranes are poorly affinity with liquid electrolytes, the need to improve the ionic conductivity, and the mechanical strength is in need of research to improve this situation is urgently needed.

The present invention has been made to solve the above problems, an object of the present invention is finally a multi-layer polyolefin separator for lithium secondary battery with a high short-circuit temperature of the membrane of the layer B / A / B layer, improved film strength at high temperature It is to provide a method for producing and a multilayer polyolefin separator for a lithium secondary battery prepared therefrom.

The above and other objects and advantages of the present invention will become more apparent from the following description of the preferred embodiments with reference to the accompanying drawings.

The above object is, in the method for producing a multilayer polyolefin separator for a lithium secondary battery, a vinylidene fluoride-based polymer is easily kneaded with a polyolefin using a compatibilizer, and a mixture thereof is combined with a liquid paraffin. Forming a layer of a vinylidene fluoride-based polymer in the form of A, forming a layer B by kneading polypropylene and liquid paraffin, layer A and layer B and layer B / A / B Co-extrusion and casting to a structure, coaxially stretching the cast sheet to prepare a separator, and washing the biaxially stretched separator with a volatile solvent to remove liquid paraffin from the biaxially stretched separator. And opening and cleaning the washed biaxially stretched separator for the lithium secondary battery. It is achieved by the method of the polyolefin membrane.

Preferably, The polyolefin and polypropylene forming the A and B layers have a weight average molecular weight of 300,000 to 600,000, and the vinylidene fluoride-based polymer has a weight average molecular weight of 50,000 to 500,000.

Preferably, Mw / Mn (weight average molecular weight / number average molecular weight) of the polyolefin forming the A layer, the vinylidene fluoride series polymer, and the polypropylene forming the B layer is 4 to 8.

Preferably, the vinylidene fluoride-based polymer forming the A layer is characterized in that it contains 10 to 60% by weight of the total weight of the polyolefin-vinylidene fluoride-based polymer composition.

Preferably, the polyolefin-vinylidene fluoride-based polymer composition forming the layer A and the liquid paraffin are characterized in that the weight ratio of 3-7: 7-3.

Preferably, the polypropylene and the liquid paraffin forming the B layer is characterized in that the weight ratio of 3-7: 7-3.

Preferably, the compatibilizer for forming the A layer is aluminum stearate, and the aluminum stearate contains 3 to 30% by weight based on the total weight of the polyolefin-vinylidene fluoride-based polymer. Characterized in that.

Preferably, the vinylidene fluoride-based polymer forming the layer A is polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, or At least one of the mixture is characterized in that.

In addition, an object of the present invention is achieved by a multilayer polyolefin separator for a lithium secondary battery prepared according to the above production method.

According to the present invention, a vinylidene fluoride-based polymer is introduced to form an A layer, and a polypropylene is used to form a B layer, so that the separation layer of the B layer / A layer / B layer has a high short circuit temperature at high temperature. It has the effect of being able to manufacture a multilayer polyolefin separator for lithium secondary battery with improved membrane strength.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. These examples are only presented by way of example only to more specifically describe the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples. .

1 is a schematic diagram showing a cross section of a multilayer polyolefin separator for a lithium secondary battery according to the present invention.

In the method for preparing a multilayer polyolefin separator for a lithium secondary battery according to the present invention, a vinylidene fluoride-based polymer as an A layer is introduced to explain a method for preparing a separator.

First, the vinylidene fluoride-based polymer is mixed using a compatibilizer to easily knead the polyolefin. Here, it is preferable to use aluminum stearate as a compatibilizer used for good kneading of the vinylidene fluoride-based polymer and polyolefin. The vinylidene fluoride-based polymer is preferably 10 to 60% by weight, more preferably 20 to 50% by weight of the total amount of the polyolefin-vinylidene fluoride-based polymer composition. In this case, the polyolefin has a weight average molecular weight of 300,000 to 600,000, and the vinylidene fluoride-based polymer preferably uses a polymer having a weight average molecular weight of 50,000 to 500,000.

In addition, Mw / Mn (weight average molecular weight / number average molecular weight) of the polyolefin and the vinylidene fluoride series polymer is less than 10, preferably 4 to 8. This is because, when Mw / Mn is 10 or more, the solubility becomes good, but the strength improvement of the resulting separator is insufficient.

As the polyolefin used in the method for producing a multilayer polyolefin separator for a lithium secondary battery according to the present invention, a crystalline homopolymer or copolymer obtained by polymerizing ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, or the like Can be mentioned. In addition, various additives such as antioxidants, ultraviolet absorbers, lubricants, antiblocking agents, pigments, dyes, inorganic fillers, and the like may be added to the polyolefins without departing from the object of the present invention.

In addition, the vinylidene fluoride-based polymer used in the method for producing a multilayer polyolefin separator for a lithium secondary battery according to the present invention is a polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, vinylidene fluoride and tetra Separation membranes can be prepared by selectively combining at least one polymer of fluoroethylene or a mixture thereof in any order.

Next, the mixture is mixed with the liquid paraffin to dissolve in the mixing step. When the polyolefin-vinylidene fluoride polymer composition is dissolved in liquid paraffin, the polyolefin-vinylidene fluoride polymer composition and the liquid paraffin are preferably in a weight ratio of 3 to 7: 7 to 3, wherein the dissolved The solution is extruded and cast at high temperature to make a sheet.

The polyolefin-vinylidene fluoride series polymer solution used as the raw material in the present invention is prepared by heating and dissolving the polyolefin-vinylidene fluoride series polymer in a solvent. Such solvent is not particularly limited as long as it can sufficiently dissolve the polyolefin-vinylidene fluoride series polymer. For example, aliphatic or cyclic hydrocarbons such as nonane, decane, undecane, dodecane, liquid paraffin, or mineral oils with boiling points corresponding thereto may be used. In order to obtain, a nonvolatile solvent such as liquid paraffin is preferable. Several properties are contemplated, such as the boiling range of suitable inert solvents such as liquid paraffin. The heat dissolution is carried out by stirring at a temperature at which the polyolefin is completely dissolved in a solvent or by a method of homogeneously mixing and dissolving the polyolefin in an extruder. In the case of dissolving while stirring in a solvent, the temperature varies depending on the polymer and the solvent used. For example, in the case of polyethylene, the temperature is in the range of 140 to 250 ° C. When preparing a membrane from a high concentration solution of polyolefin, it is preferable to dissolve in an extruder. When melt | dissolving in an extruder, the above-mentioned polyolefin is first supplied to an extruder which has a side feeder etc., and is melted. It is necessary to supply a liquid solvent to the molten polyolefin from the side feeder with respect to this molten polyolefin. When a polyolefin containing a high molecular weight polyolefin and a solvent are supplied at the same time, since the viscosity difference is large, they cannot be mixed and the screw of the polyolefin and the extruder can be rotated at the same time to prepare a solution. In heating dissolution, it is preferable to add an antioxidant for preventing oxidation of the polyolefin-vinylidene fluoride series polymer.

Next, the manufacturing method of the polypropylene separator which is B layer in the manufacturing method of the multilayer polyolefin separator for lithium secondary batteries which concerns on this invention is as follows.

The B layer is formed by kneading polypropylene and liquid paraffin, wherein the polypropylene has a weight average molecular weight of 300,000 to 600,000, and Mw / Mn (weight average molecular weight / number average molecular weight) is 4 to 8. It is done. In addition, the polypropylene and the liquid paraffin is characterized in that 3 to 7: 7 to 3 by weight.

Next, using the formed layer A and layer B, the layer B / A layer / B layer heating solution is preferably co-extruded from the die and molded. As the die, a sheet die having a mold shape having a rectangular inlet is used. A double cylindrical inflation die may be used. When the sheet die is used, the die cap is usually 0.1 to 5 mm, and the extrusion concentration is 140 to 250 ° C. The extrusion speed at this time is 20-30 cm / min. In this way, the solution extruded from the die is formed into a molded product in a gel-like state by cooling. Cooling is preferably performed at a rate of 50 ° C./minute or more up to at least the gelling temperature. In general, when the cooling rate is slow, the higher-order structure of the composition in a gel-like state becomes rougher, and the pseudo cell units forming the higher-order structure become larger, but when the cooling rate is faster, they become dense cell units. If the cooling rate is less than 50 ° C / min, the degree of crystallinity is increased to form a gel-like composition suitable for stretching. Therefore, by adjusting the cooling rate, it is possible to change the pore diameter of the resulting membrane. As the cooling method, cold air, cooling water, a method of making direct contact with another cooling medium, a method of contacting a roll cooled as a refrigerant, or the like can be used. In addition, the solution extruded from the die may be taken out before the cooling or during the cooling as a drawing ratio of 1 to 10, preferably 1 to 5. If the take-out ratio is 10 or more, it is not preferable because the tightening force is increased and it is easy to break when stretching.

The sheet made of the B layer / A layer / B layer thus prepared is stretched in at least one axial direction to produce a stretched film. The stretching method is not limited to this, but a tentering method, a roll method, a calendering method, or the like can be used. Among these methods, simultaneous biaxial stretching by the tentering method is preferable. The stretching temperature is from room temperature to the melting point of the polymer gel, preferably 80 to 130 ° C, more preferably 100 to 125 ° C. The stretching ratio is 4 to 200 times, preferably 8 to 100 times, and more preferably 16 to 50 times in terms of area.

The separation layer consisting of the B layer / A layer / B layer through the above process to remove the remaining liquid paraffin by washing with a solvent. As the washing solvent, hydrocarbons such as pentane, hexane and heptane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, and volatile hydrocarbons such as trifluoride ethane, ethyrs such as diethyl ether and dioxane can be used. These solvents are appropriately selected depending on the solvent used for dissolving the polyolefin, and used alone or in combination. The washing method is performed by a method of immersion in a solvent, a method of spraying a solvent, a method of combining them, or the like.

The cleaning as described above is performed until the liquid paraffin in the stretched molding is less than 1% by weight. Thereafter, the cleaning solvent may be dried. The drying method of the cleaning solvent may be performed by heating drying, drying by hot air, contact with a heating roll, or immersion in a heating medium. It is preferable to heat-set a dry extending | stretching composition in the temperature range of crystal dispersion temperature-melting | fusing point. If the heat setting temperature exceeds the melting point, the resin will melt. Although the time of heat setting treatment changes with heat setting temperature, it is preferable to carry out for 10 second-10 minutes.

The separator composed of the B-layer / A-layer / B-layer manufactured by the method for preparing a multilayer polyolefin separator for a lithium secondary battery according to the present invention described above is preferably a separator having a porosity of 30 to 95% and a thickness of 25 μm. Preferably 2000 seconds / 100 cc or less, more preferably 200-1000 seconds / 100 cc, the average pore diameter is preferably 0.005 ~ 1㎛, more preferably 0.01 ~ 0.2㎛, tensile strength is preferably 800 kg / Cm 2 or more, more preferably 900kg / cm 2 or more, and the puncture strength is preferably 450g or more.

In addition, the thickness of the separator of the polyolefin-vinylidene fluoride series is appropriately selected, but is preferably about 0.1 to 50 μm, more preferably 1 to 25 μm. It is because the thickness is not practical because the mechanical strength of the film is less than 0.1 mu m, and when the thickness exceeds 50 mu m, the thickness is so thick that the effective resistance becomes large. It is preferable that the thickness of the said B layer is about 1-10 micrometers.

Hereinafter, this invention is shown concretely by the following Example and a comparative example. However, the scope of the present invention is not limited by these.

EXAMPLE

The vinylidene fluoride-based polymer and polypropylene of the present invention will be described in detail with reference to a method of preparing a separator.

First, a vinylidene fluoride-based polymer having a weight average molecular weight (Mw) of 50,000 to 500,000 and a polyolefin having a weight average molecular weight (Mw) of 300,000 to 600,000 are mixed using aluminum stearate as a compatibilizer. After dissolving the mixture in liquid paraffin, the dissolved solution is extruded and cast at a high temperature to prepare a polyolefin-vinylidene fluoride-based polymer sheet. In this case, the vinylidene fluoride-based polymer is 10 to 60% by weight, more preferably 20 to 50% by weight of the total amount of the polyolefin-vinylidene fluoride-based polymer composition, aluminum stearate as a compatibilizer (aluminum) stearate) is added in an amount of 3 to 30% by weight based on the total amount of the polyolefin-vinylidene fluoride-based polymer. When the polyolefin-vinylidene fluoride-based polymer composition is dissolved in liquid paraffin, the polyolefin-vinylidene fluoride-based polymer composition and liquid paraffin are preferably in a weight ratio of 3-7: 7-3, and the dissolved solution Sheets are produced by extrusion and casting at high temperature. In heating dissolution, it is preferable to add an antioxidant for preventing oxidation of the polyolefin. Subsequently, in the forming process of the step, the B layer is coextruded from a T-die through a feed block on both sides of the A layer manufactured in the above step, stacked in a B layer / A layer / B layer structure and cooled to B The gel composition of layer / A layer / B layer structure can be obtained. The heating solution of this polyolefin is preferably molded by extruding from a die. As the die, a sheet die having a mold shape having a rectangular inlet is used. A double cylindrical inflation die may be used. When the sheet die is used, the die cap is usually 0.1 to 5 mm, and the extrusion concentration is 140 to 250 ° C. The extrusion speed at this time is 20-30 cm / min. In this way, the solution extruded from the die is formed into a molded product in a gel-like state by cooling. Cooling is preferably performed at a rate of 50 ° C./minute or more up to at least the gelling temperature.

The polyolefin-vinylidene fluoride series sheet thus prepared is subjected to simultaneous biaxial stretching by the tentering method to prepare a separator. The stretching temperature is from room temperature to the melting point of the polymer gel, preferably 80 to 130 ° C, more preferably 100 to 125 ° C. The stretching ratio is 4 to 200 times, preferably 8 to 100 times, and more preferably 16 to 50 times in terms of area.

The polyolefin-vinylidene fluoride-based separator that has undergone the above process removes residual liquid paraffin using a solvent. As the washing solvent, hydrocarbons such as pentane, hexane and heptane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, and fluorocarbons such as ethane trifluoride, and ethyr such as diethyl ether and dioxane can be used. These solvents are appropriately selected depending on the solvent used for dissolving the polyolefin, and used alone or in combination. The washing method is performed by a method of immersion in a solvent, a method of spraying a solvent, a method of combining them, or the like. The cleaning as described above is performed until the liquid paraffin in the stretched molding is less than 1% by weight. Thereafter, the cleaning solvent may be dried. The drying method of the cleaning solvent may be performed by heating drying, drying by hot air, contact with a heating roll, or immersion in a heating medium. It is preferable to heat-set a dry extending | stretching composition in the temperature range of crystal dispersion temperature-melting | fusing point. If the heat setting temperature exceeds the melting point, the resin will melt. Although the time of heat setting treatment changes with heat setting temperature, it is preferable to carry out for 10 second-10 minutes.

Example 1

The polyethylene-polyvinylidene fluoride polymer composition consisting of 50% by weight of polyvinylidene fluoride and 50% by weight of vinylidene fluoride-based polymer constituting A layer and aluminum stearate as a compatibilizer The polyethylene-polyvinylidene fluoride polymer composition was added by 6% by weight to the total amount and mixed. In addition, the polyethylene-polyvinylidene fluoride polymer composition and liquid paraffin were used in an A ratio of 4: 6. The polypropylene and liquid paraffin constituting the B-layer were 62% by weight and 38% by weight, respectively, and then coextruded and cast at high temperature, and coaxially stretched at 5ⅹ5 magnification. After the final membrane was prepared.

Example 2

A final separation membrane was manufactured in the same manner as in Example 1, except that the polypropylene and the liquid paraffin constituting the B layer were 55 wt% and 45 wt%, respectively.

Example 3

A final separation membrane was manufactured in the same manner as in Example 1, except that polypropylene and liquid paraffin constituting the B layer were made at a ratio of 48 wt% and 52 wt%, respectively.

Comparative Example 1

The final separator was manufactured in the same manner as in Example 1, except that the polymer forming the B layer was replaced with polyethylene.

Comparative Example 2

A final separator was manufactured in the same manner as in Example 2, except that the polymer constituting the B layer was replaced with polyethylene.

Comparative Example 3

A final separator was prepared in the same manner as in Example 3, except that the polymer forming the B layer was replaced with polyethylene.

The components and compositions of the Examples and Comparative Examples are shown in Tables 1 and 2 below.

 Table 1

Item A floor B floor a-b polymer (100% by weight) Compatibilizer (compared to 100% by weight of a-b polymer) a-b polymer composition: liquid paraffin (ratio)   b ’ d matter a b c Example 1 50 50 6 4: 6 62 38 Example 2 50 50 6 4: 6 55 45 Example 3 50 50 6 4: 6 48 52

[Table 2]

Item A floor B floor a-b polymer (100% by weight) Compatibilizer (compared to 100% by weight of a-b polymer) a-b polymer composition: liquid paraffin (ratio) b d matter a b c Comparative Example 1 50 50 6 4: 6 62 38 Comparative Example 2 50 50 6 4: 6 55 45 Comparative Example 3 50 50 6 4: 6 48 52

a: polyvinylidene fluoride, b: polyethylene.

c: aluminum stearate, b ': polypropylene.

    d: liquid paraffin

Experimental Example

According to the present invention, A layer is prepared using polyvinylidene fluoride, a vinylidene fluoride-based polymer, and aluminum stearate, a compatibilizer, and a B layer is prepared, using a polypropylene polymer. The properties of the separator according to the comparative example in which the separator and the B layer of the examples were made of polyethylene instead of polypropylene were measured and the results are shown in Table 3.

TABLE 3

Short circuit temperature at high temperature (℃) High temperature punching strength (N / ㎛) Example 1 148 0.011 Example 2 147 0.010 Example 3 145 0.008 Comparative Example 1 142 0.006 Comparative Example 2 142 0.005 Comparative Example 3 141 0.003

According to Table 3, it can be seen that in the case of the embodiments according to the present invention, the short circuit temperature is higher than that of the comparative example, and the film strength is improved at high temperature. This can be said to be a possible result by manufacturing the B layer formed from polypropylene, and forming a separator in the structure of B layer / A layer / B layer.

1 is a schematic diagram showing a cross-section of a separator prepared according to the method for producing a multilayer polyolefin separator for a lithium secondary battery according to the present invention.

Claims (9)

In the method of manufacturing a multilayer polyolefin separator for lithium secondary battery, Using a compatibilizer to easily knead the vinylidene fluoride series polymer with the polyolefin, and a mixture thereof with the liquid paraffin to form an A layer in the form of a polyolefin-vinylidene fluoride series polymer; Forming a layer B by kneading the polypropylene with the liquid paraffin; Co-extrusion and casting the layer A and layer B into a structure of layer B / A / B; Simultaneously biaxially stretching the cast sheet to produce a separator; Washing the biaxially stretched separator with a volatile solvent to remove liquid paraffin from the biaxially stretched separator; And heat-setting the washed biaxially stretched separator, the method of manufacturing a multilayer polyolefin separator for a lithium secondary battery . The method of claim 1, The polyolefin and polypropylene forming the A and B layers have a weight average molecular weight of 300,000 to 600,000, and the vinylidene fluoride-based polymer has a weight average molecular weight of 50,000 to 500,000, wherein the multilayer polyolefin separator for a lithium secondary battery Manufacturing method. The method of claim 1, Mw / Mn (weight average molecular weight / number average molecular weight) of the polyolefin forming the A layer, the vinylidene fluoride series polymer, and the polypropylene forming the B layer is 4 to 8, characterized in that the multilayer for a lithium secondary battery Method for producing a polyolefin separator. The method of claim 1, The vinylidene fluoride-based polymer forming the A layer is contained in 10 to 60% by weight of the total weight of the polyolefin-vinylidene fluoride-based polymer composition, a method for manufacturing a multilayer polyolefin separator for a lithium secondary battery. The method of claim 1, The polyolefin-vinylidene fluoride-based polymer composition for forming the A layer and the liquid paraffin are 3 to 7: 7 to 3 by weight ratio, the method for producing a multilayer polyolefin separator for a lithium secondary battery. The method of claim 1, The polypropylene forming the B layer and the liquid paraffin is characterized in that the weight ratio of 3 to 7: 7: 7 to 3, the method for manufacturing a multilayer polyolefin separator for lithium secondary battery. The method of claim 1, Compatibilizer for forming the A layer is aluminum stearate (aluminum stearate), characterized in that the aluminum stearate contains 3 to 30% by weight relative to the total weight of the polyolefin-vinylidene fluoride-based polymer, Method for producing a multilayer polyolefin separator for lithium secondary battery. The method of claim 1, The vinylidene fluoride-based polymer forming the layer A is at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, or a mixture thereof. Method for producing a multilayer polyolefin separator for lithium secondary battery, characterized in that one. A multilayer polyolefin separator for a lithium secondary battery, characterized in that prepared according to any one of claims 1 to 8.

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