KR20150026553A - Separator for lithium secondary battery and preparation method thereof - Google Patents

Abstract

The present invention relates to a separator for a lithium secondary battery including ultra high density polyolefin and, more particularly, to a separator for a lithium secondary battery and a manufacturing method thereof, capable of preventing a fine pore from being closed by improving the heat resistance and the reliability of a product by depositing non-oxide inorganic material on the polyolefin separator with the fine pore using a vacuum deposition method.

Description

TECHNICAL FIELD [0001] The present invention relates to a separator for a lithium secondary battery, and a separator for a lithium secondary battery,

The present invention relates to a separator for a lithium secondary battery including an ultra-high density polyolefin and a method of manufacturing the separator.

Polyolefin microporous films are widely used as battery separators because of their chemical stability and excellent physical properties.

A casting method in which a raw material is melted / injected at a high temperature is widely used as a method of making such a separator sheet, and the average thickness is 20 μm. Further, pores having a diameter of 100 nm or less are uniformly formed in a proportion of 45% or less in the entire membrane by stretching the injected separation membrane in the primary direction, which is the longitudinal axis direction, or in the secondary direction, which is the transverse axis direction after the primary drawing. If the pores of the separator are not uniform, a high resistance may be generated in a specific region to increase the temperature. In addition, when the pores are formed to have a pore size of 100 nm or more, other materials besides Li ions can move between the cathode and the anode, and shutdown of the separator becomes difficult when the temperature of the separator rises.

On the other hand, there is stability against heat shrinkage due to the characteristics required in the separator. That is, when the secondary battery is heated, the temperature may be increased to 150 to 160 ° C., and when the separator shrinks, the electrolyte moves freely to both ends, and a rapid temperature rise occurs due to a large amount of chemical reactions. It is important to improve the heat resistance of the membrane because it causes fire or explosion and causes problems in the reliability of the product.

Therefore, in order to prevent the above problems and improve the heat resistance, a method of dip-coating a PVDF-HFP binder or an inorganic material such as Al ₂ O ₃ , SiO ₂ , and TiO ₂ on the surface of a separation membrane is generally utilized.

That is, in case of the currently used coating method, powder is formed in the form of nano powder for coating, and then the coating is performed by dip coating method by mixing with binder and solvent. Therefore, the above method is required to have a high price and a complicated process for the powder. Also, a matrix material such as PVDF-HFP is used as a binder to be used, and such a binder may also cause shrinkage at high temperatures. In addition, the oxide-based minerals used in the coatings inhibit ionic conductivity or air permeability by blocking the micropores in the membrane.

In addition, the conventional dip coating method coated membranes usually increase the thickness by 6 to 10 mu m. However, since the thickness of the separator in the secondary battery exhibits an inverse relationship with the capacity of the battery, if the thickness is increased, the thermal stability is improved but the capacity of the battery is decreased.

Further, the conventional method requires additional processes for synthesizing the nano powder, the solvent and the binder in order to prepare the solution for coating, and the powder material that can be used at this time is limited due to the synthesis reaction, .

On the other hand, in the case of polypropylene, which is widely used in the production of separation membranes, microscopic pores are generated unevenly due to high crystallinity, and difficulty in inorganic coating due to low affinity with the binder.

Further, in order to coat the inorganic material, plasma or corona discharge is applied to the surface of the separator to form a -OH group on the surface of the polypropylene, thereby improving the hydrophilicity or increasing the bonding energy of the surface to improve the bonding force with the binder have.

In the case of the above method, the surface adhesion of the inorganic material is improved due to the plasma or corona discharge, but the micropores of the separation membrane are closed or the separation membrane is thermally damaged due to the heat generated during the process.

Therefore, it is necessary to develop a method for producing a new separation membrane which is excellent in heat resistance and can prevent the micropores of the separation membrane from being closed.

An object of the present invention is to provide a separator for a lithium secondary battery and a method of manufacturing the separator, which does not increase the thickness while improving the heat resistance and does not require additional additional material synthesis for coating.

Another object of the present invention is to provide a separator for a lithium secondary battery capable of suppressing microporous closure generated in a plasma / corona discharge process for enhancing adhesion between a binder and a polyolefin together with formation of uniform micropores and a method for manufacturing the separator .

In order to achieve the above object,

Polyolefin separator; And

And an inorganic material vacuum-deposited on the polyolefin separating membrane,

Wherein the inorganic material comprises at least one selected from the group consisting of CaCO ₃ , BaSO ₄ , SiPO ₄ , TiN, SiC, SBT, BLT, PZT, BaLaTiO and SrBaTiO.

The thickness of the vacuum deposited inorganic material may be 100 nm to 5 탆.

In addition, the vacuum deposited inorganic material may penetrate into the interior of the polyolefin separator to a depth of 10 nm to 10 탆.

The vacuum deposition is preferably performed using a sputtering apparatus or a chemical vapor deposition method.

In the inorganic material, PZT is PbZrTiO _{3 in} which the content ratio of Pb is 0 or more and 20 mol% or less based on the molar percentage of the total metal elements, and the sum of the sum of the Zr and Ti is 20 mol% or less, and BaLaTiO and SrBaTiO The elemental proportions of the metal elements Ba, La and Ti are preferably less than 20 mol% based on the mol% of the total metal elements.

The polyolefin separator may further include an inorganic or imide resin. In this case, the inorganic material may be at least one selected from the group consisting of SiO ₂ , TiO ₂ , Al ₂ O ₃ , BaSO ₄ and CaCO ₃ .

The separation membrane for a lithium secondary battery may have an air permeability of 300 to 1000 s / 100 cc and an ion conductivity of 0.3 to 1.0 mS / cm ² .

Further, according to another embodiment of the present invention,

Extruding and casting a polyolefin to produce a sheet;

Stretching the sheet to produce a microporous polyolefin separator; And

And vacuum depositing an inorganic material on the surface of the polyolefin separator having the micropores formed therein,

The step of vacuum-depositing the inorganic material may include:

Depositing a target inorganic material on the microporous polyolefin separator using a sputtering or chemical vapor deposition method,

Wherein the inorganic material includes at least one selected from the group consisting of CaCO ₃ , BaSO ₄ , SiPO ₄ , TiN, SiC, SBT, BLT, PZT, BaLaTiO and SrBaTiO.

Further, the step of producing the sheet may further include mixing the polyolefin and the inorganic material, and melting, compressing and casting the same to produce a sheet.

Further, after the step of producing the sheet, the sheet is stretched to produce a polyolefin separating membrane having micropores of 100 mu m or more, and the polyolefin separating membrane is subjected to plasma or corona discharge treatment to reduce the micropores to 100 mu m or less As shown in FIG.

The polyolefin may be at least one selected from the group consisting of polypropylene, polyethylene, polypropylene terephthalate, polyethylene terephthalate and polybutylene terephthalate.

According to the present invention, the non-oxide-based inorganic material deposited on the polyolefin separating film imparts heat resistance to prevent the separating film from being shrunk even when the temperature of the battery is increased. In addition, the present invention can provide better air permeability than when an inorganic oxide layer is deposited, thereby improving battery efficiency.

In addition, the present invention further improves the reliability of the product by forming more uniform micropores by further mixing the inorganic material in the separation membrane before the deposition of the non-oxide-based inorganic substance and further performing plasma or corona discharge in the separation membrane, / The corona discharge process has the effect of restricting the micropores from being closed by further imparting heat resistance to the separator.

FIG. 1 illustrates a sputtering apparatus used in a process for producing a separation membrane according to an embodiment of the present invention. Referring to FIG.
FIG. 2 illustrates a process of manufacturing a separation membrane according to an embodiment of the present invention. Referring to FIG.
3 is a cross-sectional view of a separation membrane according to an embodiment of the present invention.
4 is an electron microscope photograph showing the penetration of sputtered inorganic particles in the surface polyolefin structure of the separator of Example 1. Fig.
FIG. 5 shows a state in which an inorganic material is deposited and coated stably on the surface of the polyolefin separating membrane of Example 2. FIG.

Hereinafter, a separation membrane for a lithium secondary battery according to an embodiment of the present invention and a method of manufacturing the same will be described in detail.

According to an embodiment of the present invention, a polyolefin separator; And the vacuum-deposited inorganic material on the polyolefin separation membrane; wherein the said minerals containing CaCO _3, BaSO _4, SiPO _4, TiN, SiC, SBT, BLT, PZT, 1 or more selected from the group consisting of BaLaTiO and SrBaTiO , And a separator for a lithium secondary battery.

The present invention relates to a separator for a lithium secondary battery including an ultra-high density polyolefin and a method of manufacturing the separator. More specifically, the present invention aims to improve heat resistance by vacuum evaporation of a non-oxide-based inorganic material to a polyolefin by a dry method such as sputtering.

At this time, the separation membrane of the present invention is intended to include a coating film, and such a coating film can be deposited from an inorganic target in powder, ceramic or metal form.

Accordingly, since the present invention does not require a process of manufacturing nano powder or mixing with a binder material, the process can be reduced and the production cost for the nano powder can be reduced. Further, heat resistance is improved even at high temperatures, and inorganic particles are infiltrated into the polyolefin separator to block the pores and minimize the migration of ions. That is, in the case of the present invention, since the inorganic material is deposited and deposited in the separation membrane, the adhesion between the separation membrane and the coating film is improved compared with the conventional coating method. Therefore, the present invention exhibits remarkably improved heat resistance, ion conductivity and air permeability as compared with the conventional wet and oxide coating.

In the separator according to the present invention, the inorganic material may include CaCO ₃ , BaSO ₄ , SiPO ₄ , TiN, SiC, strontium bismuth tantalite (SBT), bismuth lanthanum titanate (BLT), lead zirconate titanate (PZT), BaLaTiO and SrBaTiO , And the like. The inorganic material is a non-oxide-based inorganic material and improves heat resistance and ion conductivity (air permeability) as compared with conventional wet and oxide coatings.

In the inorganic material, PZT is PbZrTiO _{3 in} which the content ratio of Pb is 0 or more and 20 mol% or less based on the molar percentage of the total metal elements, and the sum of the raw consumption of Zr and Ti is 20 mol% or less. In SrBaTiO 3, the elemental ratio of the metal elements Ba, La, and Ti is preferably less than 20 mol% based on the molar percentage of the total metal elements.

In addition, the thickness of the vacuum deposited inorganic material may be 100 nm to 5 占 퐉.

The vacuum deposited inorganic material may be formed on at least one surface of the polyolefin separator. The vacuum deposited inorganic material may be penetrated into the polyolefin separator to a depth of 10 nm to 10 탆. Accordingly, as described above, since the inorganic material used in the present invention is evenly deposited to the inside of the polyolefin separating film, the air permeability and adhesion can be improved compared to the conventional case.

At this time, the vacuum deposition is not a wet process such as a conventional dip coating, but a dry process. Preferably, the vacuum deposition is performed using a sputtering apparatus or a chemical vapor deposition method.

The polyolefin separator may further include an inorganic or polyimide resin. In this case, the inorganic material may be SiO ₂ , TiO ₂ , Al ₂ O ₃ , BaSO ₄ and CaCO ₃ And may be at least one selected from the group consisting of

The separator for a lithium secondary battery of the present invention may have an air permeability of 300 to 1000 s / 100 cc and an ion conductivity of 0.3 to 1.0 mS / cm ² .

On the other hand, according to another embodiment of the present invention, there is provided a method for producing a sheet, comprising extruding and casting a polyolefin to produce a sheet; Stretching the sheet to produce a microporous polyolefin separator; And vacuum depositing an inorganic material on the surface of the polyolefin separator having the micropores formed therein. The step of vacuum-depositing the inorganic material may include a step of subjecting the target inorganic material to a microporous polyolefin separator using a sputtering or chemical vapor deposition Wherein the inorganic material comprises at least one selected from the group consisting of CaCO ₃ , BaSO ₄ , SiPO ₄ , TiN, SiC, SBT, BLT, PZT, BaLaTiO, and SrBaTiO. Is provided.

In the present invention, a ferroelectric layer such as PZT, BLT, SBT, or the like is deposited using a sputtering apparatus or a chemical vapor deposition method.

In the present invention, since the inorganic material for dry deposition uses a non-oxidized inorganic material, the air permeability of the separation membrane at the time of coating has a better air permeability than that of the oxide membrane. The sputtered inorganic particles are deposited on the top of the thin film or incident into the separation membrane when the separation membrane and the particles collide with each other. The incident inorganic particles are present in the amorphous state inside the separator or crystallized to form grains with a size of several nanometers.

Therefore, the inorganic particles coated on the separator are improved in adhesion with the separator than the separator prepared by the general coating method, and the inorganic matter is combined with the separator without the binder, so that the heat resistance is improved more than the existing coated separator even when the temperature rises. Further, when deposited by the sputtering method, it can be applied to various materials than the conventional dip coating method, thereby providing a more economical effect.

In the present invention, according to the above-mentioned deposition method, inorganic substances can be uniformly penetrated not only on the surface of the polyolefin separating membrane but also inside the separating membrane, thereby further improving the air permeability.

At this time, the non-oxide based inorganic material includes at least one selected from the group consisting of CaCO ₃ , BaSO ₄ , SiPO ₄ , TiN, SiC, SBT, BLT, PZT, BaLaTiO and SrBaTiO. In addition, the inorganic material may include powder, ceramic or metal forms, more preferably ceramic or metal forms.

The inorganic material may be vacuum deposited to the surface and inside of the polyolefin separator having micropores formed by sputtering or chemical vapor deposition (CVD). Preferably, the inorganic material can be vacuum deposited on the separator using a sputtering method. The sputtering is a chamber-type sputtering gun into which a gas can be injected, and the configuration of the sputtering gun is not particularly limited. In addition, a chemical vapor deposition method can also be used, which is well known in the art.

Preferably, in the step of vacuum depositing the inorganic material, a gas selected from the group consisting of argon gas, oxygen and nitrogen may be supplied.

In addition, the polyolefin can be used without limitation as long as it is used in the production of a separation membrane, as is well known in the art. Examples of such polyolefins include at least one selected from the group consisting of polypropylene, polyethylene, polypropylene terephthalate, polyethylene terephthalate and polybutylene terephthalate.

Hereinafter, a method for producing a separation membrane of the present invention will be described in detail with reference to the drawings.

FIG. 1 illustrates a sputtering apparatus used in a process for producing a separation membrane according to an embodiment of the present invention. Referring to FIG.

Referring to FIG. 1, the non-oxide based inorganic target 2 is located at the upper end of the cathode electrode of the sputtering gun 3. Thereafter, the target is sputtered by the argon gas injected into the chamber. Then, the sputtered particles are deposited on the surface of the separator 1. At this time, as described above, the sputter includes a chamber provided with a means by which a gas for inducing sputtering can be injected.

The separation membrane (1) comprises a microporous polyolefin, and the polyolefin can be prepared by the following method.

The present invention forms a separator in the form of a sheet having a thickness of 600 to 1,200 μm by a casting roll in such a manner that a polyolefin is melt-extruded in an extruder. The temperature during the melt-extrusion process is preferably 100 to 250 ° C. The injected separation membrane may be formed to have micropores through the drawing process and have a thickness of about 20 탆, preferably 15 to 25 탆. Preferably, the separation membrane may have micropores of 10 to 200 nm.

Thereafter, the separator sheet having pores formed through the drawing process dry-deposits inorganic materials on the surface of the separator using the sputtering equipment described above.

The dry deposition uses a vacuum deposition method as described above. The inorganic material for deposition is deposited by sputtering the target. In this case, the target is formed as an inorganic material in the form of a ceramic, or in the form of a metal, and then the gas is supplied between the deposition processes to complete the deposition with the insulating material.

The air permeability of the separator on which such an insulation is deposited is 300 to 1,000 s / 100 cc, more preferably 300 to 700 s / 100 cc. If the air permeability is 1,000 s / 100 cc or more, ions are difficult to move for the Li-ion battery to operate as a battery, and the performance deteriorates.

On the other hand, during the sputtering process, the temperature may be raised to 80 to 230 ° C by the plasma, thereby reducing the micropores. In order to prevent this, the present invention may further mix an inorganic material in the separator.

That is, the inorganic material deposited on the separation membrane enters into the separation membrane due to the kinetic energy of the sputtering particles or forms an inorganic layer on the surface. The inorganic particles penetrated into the surface may undergo thermal crystallization due to thermal energy inside the separator. In the case of an inorganic material layer formed on the surface of the separation membrane, crystallization may be performed by receiving external thermal energy. When crystallization occurs, fine pores are formed between crystals and crystals to provide a passage through which Li ions can move. The inorganic substance thus deposited improves the heat resistance of the separator and suppresses the contraction of the separator even when the heat of the cell rises.

Thus, the step of producing the sheet may further include mixing the polyolefin and the inorganic material, and melting, compressing and casting the same to produce a sheet.

Further, after the step of producing the sheet, the sheet is stretched to produce a polyolefin separating membrane having micropores of 100 mu m or more, and plasma or corona discharge treatment is applied to the polyolefin separating membrane to reduce the micropores to 100 mu m or less As shown in FIG.

The inorganic layer exhibiting such characteristics may include an inorganic or imide resin. For example, the inorganic material may be at least one selected from the group consisting of SiO ₂ , TiO ₂ , Al ₂ O ₃ , BaSO ₄ and CaCO ₃ .

FIG. 2 illustrates a process of manufacturing a separation membrane according to an embodiment of the present invention. Referring to FIG.

2, a separator sheet is prepared by mixing a polyolefin, which is a polymer resin for the initial separation membrane, with an inorganic material for forming micropores, and melting / extruding the mixture. The sheet thus produced is subjected to a primary or secondary stretching process to form micropores, and plasma or corona discharge treatment for inorganic coating is performed. The surface of the modified separation membrane that has undergone such a process is accompanied by an inorganic coating process by vacuum deposition as described above.

3 is a cross-sectional view of a separation membrane according to an embodiment of the present invention.

3, when the stretching process is performed with the inorganic or imide resin 4 contained in the separator sheet, the micropores 5 are formed or the pores are not formed, And the mixture remains attached to the inside of the cavity.

According to a preferred embodiment, the present invention further comprises extruding and casting the inorganic or thermally stable imide resin into a polyolefin before melt extruding the polyolefin. The cast sheet is subjected to a stretching process to form pores. At this time, uniform pores having a size of 100 nm or more are formed on the separator due to uniformly mixed inorganic or imide resins. When a plasma process is performed on the separation membrane, the pores of 100 nm or more generated due to the inorganic substance contained in the separation membrane are reduced in size to 100 nm or less and the thermal damage of the separation membrane due to the inorganic matter contained in the separation membrane Can be further suppressed.

That is, the ceramic is first well mixed with the polyolefin using a twin-screw extruder, and the melt-extruded separator in the extruder is formed into a sheet having a thickness of 600 to 1,200 μm by a casting roll. The temperature during the melt-extrusion process is preferably 100 to 250 ° C.

The proportion of the inorganic material contained in the separation membrane is preferably 10 to 50% by weight, more preferably 30 to 40% by weight, based on the total weight of the separation membrane. If the content of the inorganic material is less than 10% by weight, there is a problem of uneven micropores formation. If the content of the inorganic material is more than 50% by weight, there is a problem in the function of shielding the membrane and elasticity.

The particle size of the inorganic substance present in the dry separation membrane of the present invention is most preferably 25 nm or less, and more preferably 5 to 15 nm.

In addition, after the addition of an inorganic substance to the polyolefin separating film having micropores as described above and the completion of the plasma or corona discharge treatment, the non-oxide type inorganic substance may be vacuum deposited by the above-described method.

Therefore, the separator of the present invention has high high permeability and can further improve the thermal stability by increasing the adhesion. Therefore, even if the temperature is increased to 150 DEG C or higher, the present invention can prevent an explosion or fire because it blocks a rapid temperature rise.

In addition, the present invention can provide a lithium secondary battery using a conventional method using the above separation membrane, and the manufacturing method thereof can be performed by a method well known in the art.

For example, at least one surface of a metal current collector is coated with a lithium mixed transition metal oxide to prepare a positive electrode, and a negative electrode is prepared by coating a negative electrode active material on at least one surface of the metal current collector. Thereafter, the lithium secondary battery can be manufactured by interposing the above-described separation membrane between the anode and the cathode, and injecting an electrolyte solution. Further, the lithium secondary battery may include a conventional battery case.

The lithium secondary battery manufactured according to this method includes the separator of the present invention, and thus has improved heat resistance and has no fire or explosion risk, so that it has excellent stability and excellent battery capacity.

Hereinafter, the present invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

[Example 1]

Polypropylene was melt-extruded in an extruder to prepare a sheet having a thickness of 20 占 퐉 by a casting roll. The melt process temperature was maintained at 100 ℃. The separated sheet-like separation membrane was subjected to a drawing process to prepare a separation membrane having a pore size of 20 m and a pore size of 100 nm.

Then, TiN in the form of ceramic was placed as an inorganic target on the upper side of the cathode of the sputter as shown in FIG. 1, and the sputtering was carried out by the argon gas injected into the chamber of the sputtering chamber. The thickness of the vacuum deposited inorganic material was set to be 1 탆 or less.

[Example 2]

A separation membrane was prepared in the same manner as in Example 1, except that SiC was used as the inorganic material. The thickness of the vacuum deposited inorganic material was set to be 1 μm or less.

[Comparative Example 1]

Polypropylene was melt-extruded in an extruder to prepare a sheet having a thickness of 20 占 퐉 by a casting roll. The melt process temperature was maintained at 100 ℃. The separated sheet-like separation membrane was subjected to a drawing process to prepare a separation membrane having a pore size of 20 m and a pore size of 200 nm.

Then, by using the Al ₂ O ₃ as inorganic dip-coating method to the surface of the oxide on the membrane were coated with 6㎛ thickness. Al ₂ O ₃ was used in an amount of 1 to 10 wt%, methyl isobutyl ketone was used as a solvent, and Igacure-290 was used as a curing agent. The membrane was cut into a size of 240 X 40 and then immersed in the solution for 1 minute and then dried at room temperature and room temperature for 1 hour to obtain a membrane.

[Experimental Example]

1. Evaluation of Coating Property

The surface of the separation membranes of Examples 1 and 2 was enlarged by 50,000 magnifications by surface electron microscopy and the results are shown in FIG. 4. The surface of the deposited separation membrane was photographed by a camera, and the results are shown in FIG.

In FIG. 4, it can be seen that the inorganic material (TiN) is uniformly deposited on the surface of the polyolefin separator as well as on the inside thereof. In addition, TiN was deposited on the surface of the polyolefin separator without any change in thickness due to penetration of the inorganic material into the tissue.

Further, as shown in Fig. 5, it was confirmed that an inorganic material was deposited and coated stably on the surface of the polyolefin separator.

2. Property evaluation

For Example 1 and Comparative Example 1, thermal shrinkage and gurley were measured by a general method. Table 1 shows the evaluation results of Example 1, Comparative Examples 1 to 3, and pristine in which inorganic coating did not proceed.

Coating material Heat shrinkage (%)
(1h, 105 < 0 > C) Ventilation
(s / 100cc) Wet Comparative Example 1 ZnO 1.0 596 Uncoated pure membrane 3.0 397 deflation Example 1 TiN 1.0 422.5 Uncoated pure membrane 3.5 309

The results of Table 1 show that Example 1 of the present invention is superior in heat shrinkage to an uncoated separator. In addition, although Comparative Example 1 showed air permeability equivalent to that of the present invention, it can be predicted that the thickness of the coating film is too thick to act as a factor for decreasing the capacity of the battery.

1: Membrane
2: Non-oxide based inorganic target
3: Sputtering gun
4: Inorganic or imide resin
5: Microstructure

Claims (14)

Polyolefin separator; And
And an inorganic material vacuum-deposited on the polyolefin separating membrane,
Wherein the inorganic material comprises at least one selected from the group consisting of CaCO ₃ , BaSO ₄ , SiPO ₄ , TiN, SiC, SBT, BLT, PZT, BaLaTiO and SrBaTiO.
The method according to claim 1,
Wherein the thickness of the vacuum deposited inorganic material is 100 nm to 5 占 퐉.
The method according to claim 1,
Wherein the vacuum deposited inorganic material penetrates into the interior of the polyolefin separator to a depth of 10 nm to 10 탆.
The method according to claim 1,
Wherein the vacuum deposition is performed by sputtering or chemical vapor deposition.
The method according to claim 1,
Wherein the PZT is PbZrTiO _{3 in} which the content ratio of Pb is 0 or more and 20 mol% or less based on the molar percentage of the total metal elements, and the sum of the raw consumption of Zr and Ti is 20 mol%
Wherein the elemental ratio of the metal elements Ba, La and Ti in the BaLaTiO and SrBaTiO is less than 20 mol% based on the mol% of the total metal elements.
The method according to claim 1,
Wherein the polyolefin separating film further comprises an inorganic or imide resin.
The method according to claim 6,
Wherein the inorganic material is at least one selected from the group consisting of SiO ₂ , TiO ₂ , Al ₂ O ₃ , BaSO _4, and CaCO ₃ .
The method according to claim 1,
A separator for a lithium secondary battery having an air permeability of 300 to 1000 s / 100 cc and an ion conductivity of 0.3 to 1.0 mS / cm ² .
Extruding and casting a polyolefin to produce a sheet;
Stretching the sheet to produce a microporous polyolefin separator; And
And vacuum depositing an inorganic material on the surface of the polyolefin separator having the micropores formed therein,
The step of vacuum-depositing the inorganic material may include:
Depositing a target inorganic material on the microporous polyolefin separator using a sputtering or chemical vapor deposition method,
The method according to claim ₁ , wherein the inorganic material comprises at least one selected from the group consisting of CaCO ₃ , BaSO ₄ , SiPO ₄ , TiN, SiC, SBT, BLT, PZT, BaLaTiO and SrBaTiO.
10. The method of claim 9,
Wherein the inorganic material comprises a powder, a ceramic or a metal.
The method according to claim 1,
Wherein a gas selected from the group consisting of argon gas, oxygen, nitrogen and carbon dioxide is supplied in the step of vacuum-depositing the inorganic material.
10. The method of claim 9,
The step of producing the sheet comprises:
A method for producing a separator for a lithium secondary battery, which further comprises mixing a polyolefin and an inorganic or ceramic, and melting, compressing and casting the same to produce a sheet.
13. The method of claim 12,
After the step of producing the sheet,
Further comprising a step of stretching the sheet to produce a polyolefin separating membrane having a fine pore size of 100 mu m or more and subjecting the polyolefin separating membrane to plasma or corona discharge treatment to reduce the micropores to 100 mu m or less. Way.
10. The method of claim 9,
Wherein the polyolefin is at least one selected from the group consisting of polypropylene, polyethylene, polypropylene terephthalate, polyethylene terephthalate, and polybutylene terephthalate.

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