KR20140086842A - Method for manufacturing separator, the separator, and battery using the separator - Google Patents

Abstract

The present invention relates to a method of manufacturing a separator with excellent uniformity of material properties by preventing the separator from being dried before being injected to a dryer as water is supplied to the separator before the separator is injected to the drier after a diluent is extracted from the separator during the manufacturing of the separator. More specifically, the present invention relates to a method of manufacturing a porous polyolefin-group separator which includes: formation of a sheet including a polyolefin-group resin and a diluent; extraction of the diluent from the sheet; and drying the sheet after the extraction to manufacture a separator. After the extraction of the diluent and before drying, water is supplied to the separator. Also, the present invention relates to a separator manufactured by the method described above and an electrochemical battery using the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a separator,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a separator, a separator thereof, and an electrochemical cell using the same.

A separator for an electrochemical cell means an interlayer that keeps the ion conductivity constant while isolating the positive electrode and the negative electrode from each other in the battery to enable charging and discharging of the battery.

In recent years, electrochemical cells for increasing the portability of electronic devices have become more lightweight and miniaturized, and there is a tendency to require high-output large capacity batteries for use in electric vehicles and the like. Therefore, it is required that a thin and light separating membrane is required, and at the same time, a separation membrane having excellent shape stability due to high temperature or high tension is required to improve the productivity of a high capacity battery.

It is advantageous for the separator to exhibit uniform physical properties throughout the separator in terms of improving the safety and long-term reliability of the battery. The physical properties of the membrane may vary depending on the composition of the membrane composition. However, even in the case of a separation membrane manufactured using the same composition, the physical properties of the separated separation membrane may be different according to the separation membrane production process, the process conditions at the separation membrane production, and the like. Therefore, it is important to appropriately control the separation membrane manufacturing process to produce a separation membrane having uniform physical properties throughout the separation membrane.

Korean Patent No. 10-0452784 and Korean Patent Publication No. 10-2012-0107118 disclose a prior art relating to a method of manufacturing a battery separator, but prior art related to the manufacture of the separator, including the above, can improve the heat resistance of the separator Discloses a method for improving the average physical properties of the entire separator membrane by improving the tensile strength and the like of the separator membrane and has been proposed to reduce the variation of the physical properties in the single separator membrane and thereby improve the uniformity of physical properties of the entire membrane. Has never been disclosed to anyone.

Therefore, there is a need for a method for preparing a separator having high uniformity of physical properties throughout the separator and development of a separator therefor.

Korean Registered Patent Publication B1 10-0452784 (published on June 29, 2005) Korean Patent Application Publication No. 10-2012-0107118 (published on September 28, 2012)

The present invention provides a separation membrane having excellent uniformity of physical properties by controlling not only the thickness of the separation membrane but also the variation of the tensile strength and the stinging strength, and a method for manufacturing the same.

Specifically, the present invention prevents moisture from being supplied to the separation membrane before the separation membrane is introduced into the drying apparatus after the dilution is extracted from the separation membrane to prevent the separation membrane from being dried before being introduced into the drying apparatus, And to provide a separation membrane having uniform physical properties and a method for producing the same.

Another object of the present invention is to provide an electrochemical cell improved in safety by using a separation membrane excellent in uniformity of physical properties.

The present invention prevents moisture from being supplied to the separation membrane before the separation membrane is introduced into the drying apparatus after the dilution is extracted from the separation membrane in the production of the separation membrane, An excellent separation membrane and a method for producing the same.

More specifically, according to one aspect of the present invention, there is provided a method for producing a sheet, comprising: forming a sheet containing a polyolefin-based resin and a diluent; extracting a diluent from the sheet; and drying the extracted sheet using a drying device And then supplying moisture to the separation membrane before the drying after the extraction of the diluent, and a method for producing the same.

According to another aspect of the present invention, there is provided a laminated sheet having an average thickness of 7 占 퐉 to 20 占 퐉, an average thickness deviation of 5% or less with respect to the average thickness, and an average tensile strength in the longitudinal and transverse directions of 1,500 kgf / cm ² or more and an average deviation of the tensile strength in the longitudinal direction and the transverse direction is 10% or less with respect to the average tensile strength in each direction.

According to another aspect of the present invention, there is provided an electrochemical cell including a cathode, a cathode, a polyolefin-based porous separator, and an electrolyte, wherein the separator is a polyolefin-based porous separator, which is a separator according to an example of the present invention.

The method for producing a polyolefin-based porous separation membrane according to an embodiment of the present invention exhibits an effect of providing a separation membrane having a small overall thickness and small variation in physical properties such as thickness, tensile strength and sting strength. Since the physical properties of the separator are greatly influenced by the thickness of the separator, the present invention provides an isolation membrane having uniform thickness, thereby providing a uniform and highly uniform separator.

In addition, the present invention provides an electrochemical cell having improved cell safety and prolonged lifetime by using the separation membrane.

1 is a schematic view schematically showing a process for producing a separation membrane according to an embodiment of the present invention in accordance with a process sequence.
FIG. 2 is a schematic view schematically showing a process from extraction of diluent, supply of moisture to a separation membrane using a nozzle, and drying to a drying process according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail. Those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Hereinafter, a method of manufacturing a separation membrane according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a schematic view schematically showing a method of manufacturing a separation membrane according to an embodiment of the present invention in accordance with a process sequence. FIG. 2 is a schematic view illustrating a method of manufacturing a separation membrane according to an embodiment of the present invention. FIG. 2 is a schematic view schematically showing a process of supplying moisture to a separation membrane using a nozzle before reaching a drying process using the apparatus.

The present invention prevents moisture from being supplied to the separation membrane before the separation membrane is introduced into the drying apparatus after the diluent is extracted from the separation membrane during the manufacturing process of the separation membrane, A separation membrane excellent in uniformity of physical properties is provided.

More specifically, according to one aspect of the present invention, there is provided a method for producing a sheet, comprising: forming a sheet containing a polyolefin-based resin and a diluent; extracting a diluent from the sheet; and drying the extracted sheet using a drying device And then supplying water to the separation membrane before the drying after the dilution is extracted. The present invention also provides a method for producing a polyolefin-based porous separation membrane.

The method for producing a polyolefin-based porous separator according to this embodiment comprises kneading a polyolefin-based resin and a diluent at a high temperature at which the polyolefin-based resin composition is melted to form a single phase, separating the polyolefin and the diluent from each other during cooling, A wet process may be used in which voids are formed inside. The wet process can control the thickness of the separator thinly and uniformly compared with the dry process, uniformly regulate the size of the generated pore, and advantageously produce a porous separator having better mechanical strength.

First, referring to Fig. 1, a polyolefin resin composition and a diluent are injected into an extruder and extruded. At this time, the polyolefin-based resin composition and the diluent can be simultaneously or sequentially injected into the extruder.

The polyolefin-based resin composition may be composed of at least one polyolefin-based resin alone, or may be a mixed composition containing at least one polyolin-based resin, a resin other than a polyolefin-based resin, and / or an inorganic substance.

Non-limiting examples of the polyolefin-based resin include polyethylene (PE), polypropylene (PP), polybutylene (PB), and poly-4-methyl -1-pentene, PMP). These may be used alone or in combination of two or more. That is, the polyolefin-based resin may be used alone, or a copolymer or a mixture thereof may be used. Non-limiting examples of the resin other than the polyolefin resin include polyamide (PA), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polychlorotrifluoroethylene , PCTFE), polyoxymethylene (POM), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVdF), polycarbonate (PC), polyarylate PAR), polysulfone (PSF), polyetherimide (PEI), and the like. These may be used alone or in combination of two or more.

Non-limiting examples of the inorganic substance include alumina, calcium carbonate, silica, barium sulfate and talc. These may be used alone or in combination of two or more. The type of the diluent is not particularly limited and may be any organic compound that forms a single phase with the polyolefin resin (or the mixture of the polyolefin resin and the other resin) at the extrusion temperature.

Non-limiting examples of the diluent include liquid paraffin (or paraffin oil) such as nonan, decane, decalin, liquid paraffin (LP), aliphatic such as paraffin wax, Click hydrocarbons; Phthalic acid esters such as dibutylphthalate and dioctyl phthalate; 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 oleic acid alcohol. These may be used alone or in combination of two or more. Specifically, liquid paraffin, which is an example of a low molecular weight organic substance having a molecular structure similar to that of polyolefin in the diluent, may be used. Liquid paraffin is harmless to the human body, has a high boiling point and low volatile components, so it has characteristics suitable for use as a diluent in a wet process.

Next, referring to FIG. 1, the gel phase obtained after the extrusion is cast into a sheet-form separation membrane. At this time, the stretching magnification of the separation membrane can be controlled by controlling the casting magnification. Specifically, after the extrusion, the gel phase obtained through the T-die is cast using a cooling roll to produce a sheet-form separation membrane. At this time, the casting magnification can be controlled by adjusting the speed of the cooling roll. After casting, the sheet is stretched in the machine direction (MD), and then stretched in the transverse direction (TD). At this time, longitudinal stretching and transverse stretching may be performed simultaneously according to the needs of those skilled in the art.

The diluent is then extracted from the longitudinally stretched and transversely stretched sheets. In one embodiment of the present invention, the diluent extraction can be carried out using an organic solvent. Specifically, the longitudinally stretched and transversely stretched sheets are immersed in an organic solvent in a diluent extraction apparatus, May be extracted.

The organic solvent used for the diluent extraction is not particularly limited and any solvent capable of extracting the diluent can be used. Examples of the organic solvent include, but are not limited to, methyl ethyl ketone, methylene chloride, and hexane, which have high extraction efficiency and are easy to dry. For example, When liquid paraffin is used, methylene chloride can be used as an organic solvent.

The organic solvent used in the step of extracting the diluent is highly volatile and toxic. Therefore, according to one embodiment of the present invention, water may be used to suppress the volatilization of the organic solvent.

The sheet subjected to the dilution extraction step can then be transferred to a drying apparatus and dried. The physical properties of the separator are influenced by the thickness of the separator, and the thickness of the separator should be uniform and uniform throughout to produce a separator having excellent physical properties. The thickness of the separation membrane is considerably influenced by the drying process of the separation membrane, and drying defects such as wrinkles in the separation membrane or drying unevenness may occur due to the drying process, and the thickness deviation of the manufactured separation membrane may be increased.

The sheet-like separation membrane is subjected to the dilution extraction process and then transferred to a drying apparatus to be dried. When the separation membrane is dried at a part of the separation membrane before being introduced into the separation membrane inlet of the drying apparatus, .

Specifically, when the separation membrane is partially dried during the movement of the separation membrane after the dilution extraction, the moisture content in the separation membrane is changed, and wrinkles and / or drying unevenness occurs in the separation membrane, Resulting in defective and dry defects. In case of a separation membrane in which drying failure occurs, even if full-scale drying is carried out in the drying apparatus, the degree of drying may be different depending on the region of the separation membrane, so that the thickness of the entire separation membrane may be uneven and the deviation may be severely produced.

Therefore, in the present invention, in order to prevent the pre-drying of the separation membrane before the separation membrane is introduced into the drying apparatus, it is preferable that a separation membrane is provided, which comprises extracting the diluent from the separation membrane and then supplying water to the separation membrane Of the present invention.

The water supply may be performed according to a method of supplying steam to the separation membrane, a method using spraying, or a method using a nozzle, but the present invention is not limited thereto, and a plurality of methods may be applied together.

The method of supplying steam to the separation membrane is not particularly limited in the method and any method can be applied as long as steam can be supplied to the separation membrane to suppress drying of the separation membrane. The temperature and the amount of the vapor supplied to the separator are not particularly limited. The method of supplying water to the separation membrane by spraying is not particularly limited in the method, and the size, temperature, and amount of water particles by spraying are also not particularly limited.

Referring to FIG. 2, in one aspect of the present invention, the water supply may be performed using the nozzle 11. The method of supplying water to the separation membrane using a nozzle is not particularly limited in terms of the nozzle inner diameter size, length, and shape. The amount and speed of the water supplied to the separation membrane through the nozzle are not particularly limited. However, according to one aspect of the present invention, the water can be supplied at a rate of 100 ml / sec or less and specifically at a rate of 10 to 100 ml / And more specifically from 30 ml / sec to 70 ml / sec.

The pre-drying of the separator can be effectively prevented within the above range, and the risk of the deformation of the separator shape due to the excessive pressure acting on the separator can be prevented.

According to this embodiment, the nozzle 11 may be installed in a separation membrane drying apparatus. For example, the nozzle may be installed in the drying device in a direction toward the movement path of the separation membrane so that moisture can be supplied to the separation membrane while the separation membrane having undergone the dilution extraction process is moved to the drying device, It can be installed at the periphery of the inlet.

The water supply to the separation membrane can be performed continuously or discontinuously without limitation after the extraction of the diluent from the separation membrane and before the separation membrane is introduced into the inlet of the drying apparatus. After the dilution extraction treatment, It can be continuously supplied until it is put into the inlet.

At this time, the supplied water falls into the organic solvent layer and can form an aqueous layer on the upper part of the organic solvent layer by phase separation.

The drying of the separator may be carried out through a drying device. The type of the drying apparatus is not particularly limited, and those conventionally used in this technical field can be used. A non-limiting example of a drying apparatus for the separation membrane is a dry roll. The drying apparatuses of the separation membrane including the drying roll include an inlet through which the separation membrane is introduced into the apparatus.

According to another aspect of the present invention, the separation membrane produced by the method may have an average thickness of 7 to 20 μm and an average deviation of the thickness of 5% or less with respect to the average thickness, Mu] m to 20 [mu] m, and more specifically, 12 [mu] m to 18 [mu] m, and the average deviation of the thickness may be 4% or less with respect to the average thickness.

If the overall thickness of the separator is not uniform and the deviation is large within the above range, properties of the separator may be different depending on the region of the separator, thereby reducing the stability of the separator.

In this specification, the term 'average deviation' means a value obtained by obtaining the sum of the absolute values of the deviations representing the difference between the measured value at each point and the average value of the physical properties of each physical property, As a percentage. The average deviation with respect to the physical properties can be expressed by the following Equation 1, and the smaller the average deviation, the more uniform the physical properties are.

[Formula 1]

Average deviation (%) =

In the above formula (1), n represents the number of points or the total number of samples at which the physical property is measured, Ai represents the physical property measured at each point or sample, and Aav represents the average value of the physical property.

는 각 지점에서의 측정한 물성값과 해당 물성의 평균값의 차이인 편차의 절대값의 총합을 의미한다.Also,

Means the sum of the absolute values of the deviations, which is the difference between the measured physical values at each point and the average value of the physical properties.

There is no particular limitation on the method of measuring the average thickness and the average deviation of the separation membrane, but a nonlimiting example is as follows. First, the separation membrane is divided into at least five sections in the width direction by an image section of the SEM cross section, For example, the thickness is measured at 10 different points, and the average of the measured values at each point is calculated to obtain the average thickness. For example, in the case of a membrane with a width of 500 mm, the thickness is measured at intervals of 20 mm from one end of the width to the width direction, and an average of the measured values is calculated to obtain an average thickness.

Subsequently, a deviation, which is the difference between the average thickness and the measured thickness value at each point, is calculated to obtain an average deviation according to Equation (1). Specifically, the sum of the absolute values of the deviation of thickness at each point is divided by the number of times of measurement, and is calculated as a percentage of the average thickness, and an average deviation is obtained.

The separation membrane of this embodiment may have an average tensile strength in the longitudinal and transverse directions of 1,500 kgf / cm ^{2 or} more, respectively, and an average deviation of tensile strength in the longitudinal direction and the transverse direction is 10% or less .

Specifically, the average tensile strength is 2000 kgf / cm < ² > For example, 2100 kgf / cm ^{2 or} more, and the average deviation of the tensile strength may be 8% or less, and more specifically, 6% or less.

It is possible not only to exhibit uniform strength in the above range but also to secure an adhesive force suitable for the separation membrane.

There is no particular limitation on the method of measuring the average tensile strength and the average deviation of the separator, but a non-limiting example is as follows. : Each sample was cut into a rectangular shape having a certain size (for example, 10 mm in width (MD) and 50 mm in length (TD)) at least at five different positions in the width direction of the membrane, for example, 10 different points Next, each of the above samples is mounted on a UTM (tensile tester) and the sample is squeezed up to a measurement length of 20 mm, and then the sample is pulled up and down to measure the tensile strength of each sample to obtain an average tensile strength of the measured values.

The difference between the measured average tensile strength and the value of the tensile strength of the sample obtained at each point is calculated and divided by the total number of the absolute values of the deviations at each point and is calculated as a percentage of the average tensile strength, .

The membrane of the present embodiment may have an average impingement strength of 680 kgf or more, and an average deviation of impingement strength may be 5% or less with respect to the average impaling strength.

Specifically, the average piercing strength may be 690 kgf or more, more specifically 700 kgf or more, and the average variation of the piercing strength may be 4% or less, for example, 3% or less.

It is possible not only to exhibit uniform strength within the above range but also to secure a strength suitable for the separation membrane.

There is no particular limitation on the method of measuring the average penetration strength of the separation membrane, but non-limiting examples are as follows: At least 5 or more, for example, 10 different points in the width direction and the longitudinal direction of the separation membrane, (MD) 50 mm × 50 mm (TD) 50 mm), and each specimen was prepared. Using a GATO TECH G5 instrument, the specimen was placed on a 10-cm hole. The pressing force was measured while pressing. The puncture strength of each sample cut at the different points is measured, and an average value of the measured values is calculated to obtain an average puncture strength.

The difference between the measured average sticking intensity and the value of the stamper strength of the sample obtained at each point was calculated and divided by the measured number of times of the absolute value of the deviation in each sample to calculate the percentage of the average sticking intensity, .

The separator of this embodiment may have an average air permeability of 400 sec / 100cc or less and an average air permeability of 10% or less with respect to the average air permeability.

Specifically, the average air permeability may be 370 sec / 100cc or less, and the average variation of the air permeability may be 8% or less with respect to the average air permeability, and more specifically, 6% or less.

The air permeability is measured by measuring the time taken for 100 cc of air to pass through the separator. There is no particular limitation on the method of measuring the average air permeability of the separator, but non-limiting examples are as follows: Each sample is cut into a circular shape having a certain size (for example, a diameter of 1 inch or more) at 5 or more different points, for example, 10 different points, and then the air permeability is measured using an air permeability measuring device (for example, The average air permeability is calculated by measuring the time taken for 100 cc of air to pass through the membrane using the sieve and then calculating the average of the measured values at each point.

Calculate the difference between the measured average air permeability and the air permeability value of the sample obtained at each point, divide the sum of the absolute values of the deviations at each point by the measured number, and calculate the average deviation by calculating the percentage of the average air permeability as a percentage.

The heat shrinkage measured after leaving the separator of the present embodiment at 105 ° C for 1 hour may be 5% or less in each of the transverse direction and the longitudinal direction, and may be 4% or less in each case. Specifically, the heat shrinkage ratio is 2 %, And more specifically less than 1% in the transverse direction. It is possible to secure stability by heat within the above range.

The method of measuring the above average heat shrinkage ratio is not particularly limited, but examples thereof are as follows. A uniform size at least five, for example, ten different points in the width direction of the separator (for example, MD) 50 mm × length (TD) 50 mm). Each specimen was cut, and the specimen at each point was left in an oven at 105 ° C. for 1 hour. The shrinkage degree in the MD direction and the TD direction And the average heat shrinkage rate is calculated.

The separation membrane of this embodiment may exhibit a porosity of 20 to 60%, and specifically, the porosity may be 20 to 50%. In this range, not only the air permeability is excellent but also the electrolytic solution can be sufficiently impregnated so that the performance of the battery can be improved and the strength of the separator can be maintained.

The method for measuring the porosity of the separation membrane is not particularly limited, but may be carried out, for example, in the following manner. : The volume (cm 3) and the mass (g) of each sample were determined by cutting the sample at 10 different points at 10 cm x 10 cm from the separation membrane. From the volume and mass and the density (g / cm 3) The porosity was calculated using Equation 2 of FIG.

[Formula 2]

Porosity (%) = (volume-mass / density of sample) / volume × 100

(The density of the sample = the density of the polyolefin-based resin used (e.g., polyethylene)

According to still another aspect of the present invention, there is provided an electrochemical cell including a polyolefin-based porous separator, an anode, and a cathode filled with an electrolyte. The polyolefin-based porous separator may be a separator prepared according to the above-described production method of the present invention or the above-described separator of the present invention.

Specifically, according to this aspect, there is provided an electrochemical cell comprising an anode, a cathode, a polyolefin-based porous separator, and an electrolyte, wherein the separator has an average thickness of 7 탆 to 20 탆 and an average deviation of thickness of 5% And an average tensile strength in the longitudinal direction and the transverse direction of 1,500 kgf / cm ² or more and an average deviation of the tensile strength in the longitudinal direction and the transverse direction, respectively, of 10% or less with respect to the average tensile strength in each direction do.

The type of the electrochemical cell is not particularly limited and may be a battery of a kind known in the technical field of the present invention.

The electrochemical cell of this embodiment may be a lithium secondary battery such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

The method for producing the electrochemical cell of this embodiment is not particularly limited, and a method commonly used in the technical field of the present invention can be used.

A non-limiting example of the method for producing the above-described electrochemical cell is as follows: A battery can be manufactured by placing the polyolefin-based porous separator of the present invention between a positive electrode and a negative electrode of a battery, .

The electrode constituting the electrochemical cell of this embodiment can be produced by binding an electrode active material to an electrode current collector by a method commonly used in the technical field of the present invention.

Among the electrode active materials used in this embodiment, the positive electrode active material is not particularly limited and a positive electrode active material conventionally used in the technical field of the present invention may be used.

Non-limiting examples of the positive electrode active material include lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, and lithium composite oxide in combination thereof.

Among the electrode active materials used in this embodiment, the negative active material is not particularly limited, and the negative active material conventionally used in the technical field of the present invention may be used.

Non-limiting examples of the negative electrode active material include a lithium adsorbent material such as lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite or other carbon materials, and the like .

The electrode current collector used in this embodiment is not particularly limited, and electrode current collectors commonly used in the technical field of the present invention can be used.

Non-limiting examples of the positive electrode current collector material among the electrode current collectors include aluminum, nickel, or foil produced by a combination of these materials.

As a non-limiting example of the cathode current collector material of the electrode current collector, copper, gold, nickel, a copper alloy, or a foil produced by a combination of these materials can be used.

The electrolytic solution used in this embodiment is not particularly limited, and electrolytic solutions for electrochemical cells commonly used in the technical field of the present invention can be used.

The electrolytic solution may be a salt having a structure such as A ⁺ B ^- dissolved or dissociated in an organic solvent. Non-limiting examples of the A ⁺ include alkali metal cations such as Li ⁺ , Na ^+, or K ⁺ , or cations made of combinations thereof. Non-limiting examples of B ^- include PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N ₃ SO ₂ ) ₂ ^- or C (CF ₂ SO ₂ ) ₃ ^- , or an anion composed of a combination of these.

Nonlimiting examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate Dipropyl carbonate (DPC), dimethyl sulfoxide (DMSO), acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran (THF), N-methyl- N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC) or gamma-butyrolactone (GBL). These may be used alone or in combination of two or more.

Hereinafter, the present invention will be described in more detail by describing Examples, Comparative Examples and Experimental Examples. However, the following examples, comparative examples and experimental examples are merely examples of the present invention, and the present invention should not be construed as being limited thereto.

[ Example  1 and 2] nozzles to supply water to the separation membrane Polyolefin series  Manufacturing method of porous separator

< Example  1>

30 parts by weight of high-density polyethylene (HDPE, manufactured by Mitsui Chemical Co., Ltd.) having a weight average molecular weight of 600,000 g / mol was fed to a twin-screw extruder, and then 70 parts by weight of liquid paraffin (Far East oil) Respectively.

After the extrusion, the gel phase obtained through the T-die was formed into a sheet-form separator using a cooling roll. The separator was stretched at 105 ° C in the machine direction (MD) and at 115 ° C in the transverse direction (TD) (draw ratio: 5x5).

The elongated polyethylene separator was immersed in methylene chloride (Samsung Fine Chemical) to extract liquid paraffin, and then dried and transferred to a drying roll. At this time, water was supplied to the separation membrane at a rate of 50 ml / sec from a nozzle provided under the separation membrane inlet of the drying roll, and water was continuously supplied until the separation membrane was introduced into the inlet of the drying roll.

Then, the dried film was heat-set while being stretched in the transverse direction at 130 ° C, and wound to produce a polyolefin-based porous separator having a final draw ratio of 5 × 5 in the longitudinal and transverse directions.

< Example  2>

In Example 1, 85 parts by weight of HDPE having a weight average molecular weight of 600,000 g / mol and 15 parts by weight of Ultra High Molecular Weight Polyethylene (UHMWPE, manufactured by Mitsui Chemicals) having a weight average molecular weight of 2,400,000 g / mol Was fed to a twin-screw extruder, and then a separator was produced in the same manner as in Example 1, except that 30 parts by weight of the mixed resins (HDPE and UHMWPE) were fed into a twin-screw extruder with 70 parts by weight of liquid paraffin. Respectively.

[ Comparative Example  1 &amp;le; 2] &lt; / RTI &gt; Polyolefin series  Manufacturing method of porous separator

< Comparative Example  1>

In Example 1, a separation membrane was prepared in the same manner as in Example 1, except that the step of supplying water to the separation membrane was not performed.

< Comparative Example  2>

In Example 2, a separation membrane was prepared in the same manner as in Example 2, except that the step of supplying moisture to the separation membrane was not performed.

The composition of each separation membrane according to Examples 1 and 2 and Comparative Examples 1 and 2 and the production conditions of the separation membranes are shown in Table 1 below.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Furtherance
(Parts by weight) HDPE 30 25.5 30 25.5 UHMWPE - 4.5 - 4.5 Liquid paraffin 70 70 70 70 Whether it is hydrated supply supply Not supplied Not supplied Stretching magnification 5 × 5 5 × 5 5 × 5 5 × 5

< Experimental Example  1> Appearance Evaluation of Membrane

The appearance of each of the membranes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was observed to evaluate appearance characteristics as follows. When at least one drying stain or wrinkle was observed in each membrane, it was evaluated as 'Defective', and in the case where no drying stain and wrinkle were observed in the membrane, it was evaluated as 'Excellent'.

< Experimental Example  2> Measure average thickness and average deviation of membrane

In order to measure the thickness of the separator prepared in Examples 1 and 2 and Comparative Examples 1 to 3, the following experiment was conducted.

Each of the separators prepared in the above Examples and Comparative Examples was measured for thickness at intervals of 20 mm from one end of the width of the separator using a thickness meter (Mitutoyo Litematic VL-50 model) (Aav) of each of the thickness values (A1 to A10) measured in (n) was calculated to obtain an average thickness.

Then, the difference between the thickness at each point and the average thickness is calculated, and the average of the absolute values of the deviations at each point is obtained, and the average deviation (%) as a percentage of the average thickness is shown .

[Formula 1]

Average deviation (%) =

는 각 지점에서의 측정한 물성값과 해당 물성의 평균값의 차이인 편차의 절대값의 총합을 의미한다.)(Where n is the total number of points at which the properties are measured, Ai is the physical property measured at each point, Aav is the average value of the properties,

Means the sum of the absolute values of the deviations, which is the difference between the measured values at each point and the average value of the corresponding properties).

< Experimental Example  3> Measure average tensile strength and average deviation of membrane

In order to measure the tensile strength of the separator prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the following experiment was conducted.

Each of the separation membranes prepared in the above Examples and Comparative Examples was cut into 10 rectangular pieces of 10 mm × 50 mm longitudinal (MD) pieces at 10 different points. The average tensile strength (Aav) in the MD direction and the TD direction was measured by pulling the sample so that the measurement length was 20 mm after being mounted on a UTM (tensile tester), and the tensile strength and the average tensile strength The average deviation (%) was calculated in the same manner as in Experimental Example 2.

< Experimental Example  4> Measure average sticking strength and average deviation of membrane

The following experiments were conducted to measure the penetration strength of the membranes prepared in Examples 1 and 2 and Comparative Examples 1 and 2.

The following experiments were conducted to measure the average penetration strength of the membranes prepared in Examples 1 and 2 and Comparative Examples 1 to 3.

Samples were cut at 10 different points at a constant size of 50 mm in MD (MD) and 50 mm in length (TD) in the separators prepared in the above Examples and Comparative Examples, and the samples were cut in 10 cm holes After the sample was placed on it, the force to be drilled was measured with a 1 mm probe. The puncture strength of each sample was measured to calculate the average puncture strength (Aav).

Average deviation (%) was calculated in the same manner as in Experimental Example 2, by calculating the average striking intensity and deviation of the stuck intensity of the sample obtained at each point.

< Experimental Example  5>  Measure average permeability and mean deviation of membrane

In order to measure the air permeability of each membrane prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the following experiment was conducted.

Ten samples were cut out at 10 or more different points in a circular shape having a diameter of 1 inch or more in the width direction of the separator prepared in the above examples and comparative examples, ) Was used to measure the passage time of 100 cc of air in the samples cut at each of the above points. The time was measured five times each, the average value was calculated, and the average air permeability was measured. The difference between the air permeability and the average air permeability (Aav) in each sample was calculated to obtain a deviation. (%) Was calculated.

< Experimental Example  6> Average of membrane Heat shrinkage  Measure

In order to measure the heat shrinkage of the separator prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the following experiment was conducted.

Each of the separation membranes prepared in the above Examples and Comparative Examples was cut into 10 pieces at different MD 50 mm × TD 50 mm. Each of the samples was allowed to stand in an oven at 105 DEG C for 1 hour, and the degree of shrinkage in the MD and TD directions of the samples cut at each point was measured to calculate the average heat shrinkage (Aav) in each direction.

< Experimental Example  7> Measurement of porosity of membrane

The volume (cm 3) and the mass (g) of each sample were determined by cutting the sample at 10 different points with a width of 10 cm and a length of 10 cm. The volume and mass and the density (g / cm 3) The average porosity was measured by measuring each porosity using the following formula 2. The difference between the porosity and the average porosity Aav in each sample was calculated to obtain the deviation and the average deviation %) Was calculated.

[Formula 2]

Porosity (%) = (volume-mass / density of sample) / volume × 100

(The density of the sample = the density of the polyolefin-based resin used (e.g., polyethylene)

The measurement results of the above Experimental Examples 1 to 7 are shown in Table 2 below.

Properties Example 1 Example 2 Comparative Example 1 Comparative Example 2 Exterior Great Great Bad Bad Thickness (㎛) The average value (Aav) 14 14 14 14

0.25 0.5 One One Average deviation (%) 1.79 3.57 7.14 7.14 Ventilation
(Sec / 100cc) The average value (Aav) 350 360 410 425

15 20 30 50 Average deviation (%) 4.29 5.56 7.32 11.76 Sting intensity
(gf) The average value (Aav) 695 701 660 680

15 20 40 85 Average deviation (%) 2.16 2.85 6.06 12.5 Porosity (%) The average value (Aav) 35 35 35 35

5 5 10 10 Average deviation (%) 14.29 14.29 28.57 28.57 The tensile strength
(kgf / cm ² ) MD The average value (Aav) 2210 2150 1964 2020

100 120 180 240 Average deviation (%) 4.52 5.58 9.16 11.88 TD The average value (Aav) 2100 2110 1930 2100

100 110 170 230 Average deviation (%) 4.76 5.21 8.80 10.95 Heat shrinkage
(%) MD The average value (Aav) <3 <4 <5 <5 TD Average deviation (%) <1 <1 <1.5 <3

As shown in Tables 1 and 2, in Examples 1 and 2 in which moisture was supplied to the separation membrane while the separation membrane was moved to the drying apparatus after extracting the diluent from the separation membrane, The average deviation of the thickness of the membrane was measured to be 5% or less with respect to the average thickness, and it was confirmed that the membrane having a fairly uniform thickness was manufactured.

In the case of the membranes of Examples 1 and 2 in which the thickness was uniformly formed, the membrane had excellent external appearance characteristics as well as excellent uniformity in all properties corresponding to air permeability, sting strength, porosity, tensile strength and heat shrinkage Respectively.

10 Drying unit inlet
11 Nozzle for water supply

Claims (18)

A sheet containing a polyolefin-based resin and a diluent is formed,
A diluent is extracted from the sheet,
And drying the extracted separation membrane using a drying apparatus having an inlet port to produce a separation membrane,
And supplying moisture to the separation membrane before the drying after the dilution extraction. The method of manufacturing a polyolefin-based porous separation membrane according to claim 1, wherein the water supply is performed by supplying steam. The method of manufacturing a polyolefin-based porous separation membrane according to claim 1, wherein the water supply is performed by spraying. The method of manufacturing a polyolefin-based porous separation membrane according to claim 1, wherein the water supply is performed by supplying water through a nozzle. 5. The method according to claim 4, wherein water is supplied through the nozzle at a rate of 100 ml / sec or less. The method of claim 1, wherein the moisture supply is continuously performed until the separation membrane is injected into the separation membrane inlet of the drying apparatus after the dilution extraction. The method of manufacturing a polyolefin-based porous separation membrane according to claim 1, wherein the extraction of the diluent comprises dipping the separation membrane in an organic solvent. The method of claim 1, wherein the diluent is liquid paraffin. 8. The method of claim 7, wherein the organic solvent is methylene chloride. The method for producing a polyolefin-based porous separation membrane according to claim 7, wherein an aqueous layer is formed on the upper layer of the organic solvent. The method of manufacturing a polyolefin-based porous separation membrane according to claim 1, wherein the drying apparatus is a drying roll. An average thickness of 7 mu m to 20 mu m,
The average deviation of the thickness is 5% or less with respect to the average thickness,
The mean tensile strengths in machine direction (MD) and transverse direction (TD) were more than 1,500 kgf / cm ² respectively and the average deviation of tensile strength in longitudinal and transverse direction was higher than average tensile strength in each direction A polyolefin-based porous separator of 10% or less, respectively. The polyolefin-based porous separator according to claim 12, wherein the average piercing strength of the separator is 680 kgf or more and the average piercing strength is 5% or less with respect to the average piercing strength. The polyolefin-based porous separator according to claim 12, wherein the average permeability of the separator is 400 sec / 100 cc or less and the average deviation of the air permeability is 10% or less with respect to the average air permeability. 13. The polyolefin-based porous separator according to claim 12, wherein the separator has a heat shrinkage of 5% or less in both the transverse direction and the longitudinal direction after being left at 105 DEG C for 1 hour. The polyolefin-based porous separator according to claim 12, wherein the separator has a porosity of 20 to 60%. An anode, a cathode, a polyolefin-based porous separator, and an electrolyte,
Wherein the separator is a separator of any one of claims 12 to 16, wherein the separator is a polyolefin-based porous separator. 18. The electrochemical cell of claim 17, wherein the electrochemical cell is a lithium secondary battery.

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