KR101491607B1 - Manufacturing method of organic-inorganic hybrid porous seperation membrane and organic-inorganic hybrid porous seperation membrane using the same method - Google Patents

Abstract

The present invention relates to a method for producing a porous organic / inorganic separator for a secondary battery and an organic / inorganic porous separator prepared therefrom, which comprises a porous polyolefin base material and an active site of the inorganic particles on the surface of the base material are mixed with a C ₆ to C ₃₆ fatty acid, Or an active layer coated with an organic binder polymer mixture that is modified with an oxidized wax. The porous separator according to the present invention has a strong adhesive force with a substrate than conventional separators, and can provide excellent ion conductivity and excellent cell capacity retention.

Description

Technical Field [0001] The present invention relates to a method for producing an organic / inorganic hybrid porous membrane for an organic / inorganic hybrid battery, and a porous organic / inorganic hybrid membrane prepared from the porous organic / inorganic hybrid membrane,

The present invention relates to a method for producing an organic / inorganic porous membrane for a secondary cell and an organic / inorganic porous membrane prepared therefrom.

BACKGROUND ART [0002] With the recent trend toward miniaturization and weight reduction of electronic devices, batteries used as power sources for portable electronic devices are also required to be smaller and lighter. Lithium secondary batteries have been put to practical use as batteries that are small in size and can be charged and discharged with a high capacity.

 The lithium ion battery is used not only as a power source for small electronic devices but also as an electric automobile and an electric bicycle. Accordingly, high-temperature storage characteristics and life characteristics are demanded which are even better than those required for conventional small batteries. In particular, lithium ion batteries for hybrid electric vehicles are required to have improved stability and long-term storage performance.

The lithium _secondary battery is manufactured by using a metal oxide such as LiCoO ₂ as a cathode active material and a carbon material as an anode active material and a polyolefin porous separator between the anode and the cathode and a nonaqueous electrolyte solution containing a lithium salt such as LiPF ₆ do. During charging, lithium ions of the positive electrode active material are released and inserted into the carbon layer of the negative electrode. In discharging, lithium ions of the negative electrode carbon layer are released and inserted into the positive electrode active material. In this case, As shown in FIG.

Here, the porous separator prevents physical contact between the cathode and the anode, and at the same time passes lithium ions through the pores. The separator itself does not participate in the electrochemical reaction during charging and discharging, but has porosity, It may have a great influence on the cycle performance and safety of the battery.

The polyolefin membrane used as a porous separator of the lithium secondary battery currently produced exhibits extreme thermal shrinkage behavior at a temperature of 100 ° C or more due to the characteristics of the manufacturing process including the material properties and elongation, causing a short circuit between the cathode and the anode at a high temperature It may cause a battery accident, and from the viewpoint of mechanical characteristics, the physical rupture characteristic of the separator is weak, so that there is a disadvantage in that internal short circuit of the battery is easily caused by foreign matter in the battery.

In recent years, in order to respond to the improvement of stability, researches and developments have been actively conducted on organic / inorganic composite membranes prepared by coating ceramic particles and binder polymers on polyolefin-based or polyester porous membranes, and Korean Patent Registration No. 775310 Document 1).

However, when the organic / inorganic composite membrane is used, since the adhesive force between the coating material (ceramic particles + binder polymer) and the porous substrate is weak, the coated materials easily peel off from the substrate, . In addition, the ceramic particles coated with the stress generated in the winding process of the rewinder can be removed, and the ceramic particles thus removed serve as local defects of the secondary battery, which may adversely affect the safety of the battery.

Therefore, in addition to research on the use of organic / inorganic composite membranes as separation membranes for secondary batteries, studies are being urgently needed to prevent the adhesion between the porous membrane substrate and the coating layer and the desorption of ceramic particles.

Korean Patent No. 775310

The present invention provides a separation membrane for a secondary battery, and more specifically, it has excellent mechanical and thermal characteristics and does not cause any safety deterioration due to short-circuiting between the anode and the cathode even under excessive conditions such as high temperature and overcharge, And more particularly, to provide an organic / inorganic porous separator having improved electrical characteristics and stability of the secondary battery by remarkably reducing the adhesion between the porous membrane substrate and the coating layer and the desorption of the ceramic particles.

In order to achieve the above object, the present invention provides a porous polyolefin substrate which is subjected to a plasma treatment or an acid treatment, and an organic binder which is obtained by modifying the active site of inorganic particles with a C ₆ to C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax, There is provided an organic / inorganic porous separator comprising an active layer coated with a polymer mixture.

The present invention also relates to a method for producing a porous polyolefin substrate, comprising the steps of: a) preparing an inorganic binder polymer mixture in which an active site of inorganic particles is modified with a C ₆ -C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax; b) And c) applying and drying a slurry containing at least one surface of the porous polyolefin substrate of the acid-treated or plasma-treated porous organic polyolefin substrate and the organic binder polymer mixture of a) and the solvent to form an active layer, A method for producing a separation membrane is provided.

The present invention also provides a secondary battery comprising the organic or inorganic porous separator, or the organic or inorganic porous separator produced by the production method.

The porous separator according to the present invention has excellent mechanical and thermal characteristics, and therefore, even in an excessive condition such as high temperature and overcharge, safety is not deteriorated due to short-circuiting between the anode and the cathode. Therefore, the cell characteristics are excellent, Or an organic porous membrane having improved adhesion to the porous layer substrate and coating layer due to the acid treatment and a decrease in desorption of the ceramic particles, thereby improving the electrical stability of the secondary battery.

Also, the porous separator according to the present invention has a strong adhesion to a strong substrate that can not be compared with conventional organic / inorganic composite membranes, and can provide excellent ion conductivity and excellent battery capacity retention.

The present invention relates to a porous polyolefin substrate which is subjected to a plasma treatment or an acid treatment, and an active layer coated with an organic binder polymer mixture in which active sites of inorganic particles are modified with a C ₆ -C ₃₆ fatty acid, an acrylate polymer or an oxidized wax, The present invention also provides an organic / inorganic porous separator.

The organic binder polymer mixture may include 1 to 200 parts by weight of a C ₆ to C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax based on 100 parts by weight of the inorganic particles.

(AA / HAPS) of acrylic acid and 2-hydroxy-3-allyloxy-1-propanesulfonic acid, a copolymer of acrylic acid and methyl acrylate AA / MA), a copolymer of methyl acrylate and isobutylene (MA / IB), and a copolymer of methyl acrylate and acrylic acid and vinyl acetate.

The inorganic particles may be a _{SiO 2, Al 2 O 3,} TiO 2, SnO 2, CeO 2, ZrO 2, BaTiO 3 , and Y one or more than one metal oxide selected from ₂ O _3, but are not necessarily limited to, .

The active site is not limited as long as it is capable of being modified by the C ₆ to C ₃₆ fatty acid or oxidized wax. Specifically, _{-COO, -NH 2, -CONH 2,} -PO 3 H 2, -SH, -SO 3 H, -SO 2 H, -NO 2, and _{-O (CH 2 CH 2 O)} n H ( in this case, n may be at least one or more hydrophobic groups selected from the group consisting of a hydrophilic group and aryl (aryl), a C ₃ ~ C ₃₀ alkyl group and C ₃ ~ C _30, consisting of an integer from 0 to 5).

The C ₆ to C ₃₆ fatty acid or oxidized wax is preferably a binder containing two or more fatty acid groups as terminal groups.

The secondary battery including the organic / inorganic porous separator according to the present invention is included in the scope of the present invention.

The present invention may further comprise 1 to 20 parts by weight of inorganic particles (B) per 100 parts by weight of the organic binder polymer mixture.

Further, according to the present invention,

a) preparing an organic binder polymer mixture in which the active site of the inorganic particles is modified with a C ₆ -C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax,

b) acid treatment or plasma treatment of the porous polyolefin substrate and

c) applying and drying a slurry containing the organic binder polymer mixture and solvent of the above a) on at least one side of the acid-treated or plasma-treated porous polyolefin substrate to form an active layer

The present invention also provides a method for producing an organic / inorganic porous separator.

The plasma treatment of step b) in the above production method preferably uses a plasma output in the range of 10 to 1000 W in an atmosphere of nitrogen, oxygen, air, argon or a mixture thereof.

It is preferable to use water or alcohol adjusted to pH 1 to 3 for the acid treatment.

In the step c), the solvent of the slurry dissolves a C ₆ -C ₃₆ fatty acid, an acrylate polymer or an oxidized wax, and may contain 10 to 1000 parts by weight based on 100 parts by weight of the organic binder polymer mixture.

The thickness of the active layer in (c) after drying is preferably 0.1 to 100 탆.

The organic or inorganic porous separator produced by the production method according to the present invention is included in the scope of the present invention.

The secondary battery including the organic / inorganic porous separator according to the present invention is also included in the scope of the present invention.

Hereinafter, the present invention will be described in detail.

The organic / inorganic porous separator according to the present invention is characterized in that the active layer containing the organic binder polymer mixture is formed on at least one side of the acid-treated or plasma-treated porous olefin substrate. Specifically, the present invention includes a porous polyolefin base material which is subjected to an acid treatment or a plasma treatment, and an active layer coated with a mixture of an organic binder polymer in which an active site of inorganic particles is modified with a C ₆ to C ₃₆ fatty acid or an oxidized wax on the surface of the base material The present invention relates to an organic / inorganic porous separator.

First, the porous olefin substrate subjected to acid treatment or plasma treatment will be described in detail.

The porous polyolefin substrate may be selected from a polyethylene separator, a polypropylene separator, a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene triple layer separator, and a polypropylene / polyethylene / polypropylene triple layer separator.

These porous polyolefin base materials are not particularly limited, but they preferably have a porosity of at least 30% or more, and preferably have a thickness of 10 to 300 탆. The porous polyolefin base material is preferably a microporous membrane having excellent adhesion with the organic binder polymer mixture and excellent mechanical strength It is good.

The porous polyolefin substrate is preferably hydrophobized before the active layer is formed. Therefore, the porous polyolefin substrate is characterized by using a pretreated material such as a plasma treatment or an acid treatment.

 To prepare the organic porous separator of the present invention, the porous polyolefin substrate may be acid-treated with a solution containing at least one hydrophobic material. The solvent in the solution may preferably be water, preferably an acid, preferably water adjusted to a pH of 1 to 3 with acetic acid or hydrochloric acid, and / or an alcohol, preferably ethanol. The solvent fraction due to the acid-treated water or alcohol may in each case be within the range of 0% to 100% by volume. Preferably, the solvent fraction due to water is in the range of 0 vol% to 60 vol%, and the solvent fraction due to alcohol is in the range of 40 vol% to 100 vol%. The solvent is introduced into the hydrophobic material in an amount of 0.1 to 30% by weight, preferably 1 to 10% by weight, in order to prepare a solution. Useful hydrophobic materials include, for example, the silanes mentioned above. Surprisingly, good hydrophobicity is obtained with only strong hydrophobic compounds, such as triethoxy (3,3,4,4,5,5,6,6,7,7,8,8-tridecafluorooctyl) silane Methyltriethoxysilane or i-butyltriethoxysilane is treated without any treatment, and a sufficiently favorable effect is obtained. The solution is stirred at room temperature to uniformly disperse the hydrophobic materials in the solution and subsequently to the porous inorganic layer and dried. The drying can be accelerated by treatment at a temperature within the range of 25 to 100 占 폚.

The organic-inorganic porous separator according to the present invention may be treated with another adhesion promoter such as a silane-based agent on the acid-treated porous polyolefin substrate before forming the active layer.

On the other hand, the plasma treatment will be understood to shoot a plasma beam or jet in a porous polyolefin substrate. Plasma is produced in a conventional manner by discharging a high frequency AC voltage in a gas, i.e., a working gas. A portion of this plasma is ejected out of the discharge system by utilizing the target gas stream and is ejected through the apertures onto the surface of the material to be treated through a plasma nozzle (formed by a stator rotating at high speed inside the rotor). One example of a manufacturer of a plasma generation system for plasma-treating a surface is Plasmatreat GmbH (Steinhagen D-33803 non-sambek 10).

The working gas for the plasma treatment on the porous polyolefin substrate is preferably selected from the group consisting of nitrogen, oxygen, air, argon, helium, carbon dioxide, carbon monoxide, ozone, silane, alkane, fluoroalkane, fluoroalkene, , Air, argon, or a mixture thereof. It is most preferred to use oxygen, argon, air or an oxygen-argon mixture.

It may be advantageous to use a radio frequency plasma, a cyclotron resonance frequency plasma or a microwave plasma, and it is particularly preferable to use a radio frequency plasma.

The plasma treatment may preferably use a plasma output of 10 to 1000 W, more preferably 100 to 750 W, and most preferably 300 to 500 W.

The distance between the nozzle and the polymeric nonwoven fabric in the plasma treatment may be from 0.1 to 300 mm, more preferably from 1 to 80 mm, even more preferably from 2 to 50 mm, and most preferably from 5 to 20 mm.

The plasma treatment is preferably carried out at a substrate velocity of 60 - 0.002 m / min. The rate of substrate in the context of the method of the present invention means the rate at which the surface of the porous polyolefin substrate to be treated is moved through the volume occupied by the plasma. This speed can be selected more preferably from 40 to 0.02 m / min, even more preferably from 30 to 0.2 m / min, and most preferably from 20 to 0.1 m / min.

Since the acid treatment or the plasma treatment increases the hydrophobic group of the porous polyolefin substrate, the adhesion strength with the organic binder polymer mixture in the active layer is further improved, and thus the durability of the battery is increased and the separation membrane property can be stably maintained even at a high temperature .

Next, the active layer will be described in detail.

The active layer includes an organic binder polymer mixture in which the active sites of the inorganic particles are modified with a C ₆ to C ₃₆ fatty acid or oxidized wax.

The inorganic particles, which are the active layer component of the organic / inorganic porous separator according to the present invention, serve as a kind of spacer capable of forming fine pores and maintaining the physical form by allowing void spaces between inorganic particles. Generally, even if the temperature is higher than 200 ° C, the physical properties are not changed, so that it plays a role of enhancing the heat resistance.

In addition, when considering the electrochemical stability and high dielectric constant characteristics of the dielectric constant of 5 or more, the inorganic particles may be SiO ₂ , Al ₂ O ₃ , TiO ₂ , SnO ₂ , CeO ₂ , ZrO ₂ , BaTiO ₃ and Y ₂ O ₃ , And is not necessarily limited to these.

The size of the inorganic particles is not limited, but it is preferably 0.0001 to 10 탆 in order to form a film having a uniform thickness and a proper porosity. By maintaining the physical properties of the organic / inorganic porous separator within the above range and controlling the size of the desired pore, the functionality of the internal short circuit can be reduced during charging and discharging.

Further, the inorganic particles are characterized by having active sites, and the active sites are not limited as long as they can be modified by the C ₆ to C ₃₆ fatty acids or oxidized waxes. Specifically, _{-COO, -NH 2, -CONH 2,} -PO 3 H 2, -SH, -SO 3 H, -SO 2 H, -NO 2, and _{-O (CH 2 CH 2 O)} n H ( in this case, n may be at least one or more hydrophobic groups selected from the group consisting of a hydrophilic group and aryl (aryl), a C ₃ ~ C ₃₀ alkyl group and C ₃ ~ C _30, consisting of an integer from 0 to 5). According to one embodiment of the present invention, it may have an -OH group.

The C ₆ to C ₃₆ fatty acid or oxidized wax is preferably a binder containing two or more fatty acid groups as terminal groups. When C ₆ to C ₃₆ fatty acids or oxidized waxes have two or more fatty acid groups, they form a crosslinked structure with the active sites on the surface of the inorganic substance to strengthen the bonding force between the inorganic particles. When used as a separator for secondary batteries, It is possible to remarkably eliminate the phenomenon of desorption. Further, it is excellent in adhesion to a base material, so that it is more firmly fixed to the preprocessed polyolefin base material, and durability can be further increased.

The binder may also include an organic binder polymer mixture modified with an acrylic acid polymer.

The present invention has surprisingly found that inorganic particles such as SiO ₂ are more firmly fixed to the polyolefin substrate according to the present invention when the acrylic acid-based polymer is reacted with the active group of the inorganic particles, thereby completing the present invention. The acrylic acid-based polymer is preferably an acrylic acid-based polymer containing acrylic acid and having a molecular weight of 1,000 to 100,000, but is not limited thereto.

Examples of the acrylic acid-based polymer include polyacrylic acid (AA), a copolymer of acrylic acid and 2-hydroxy-3-allyloxy-1-propanesulfonic acid (AA / HAPS), a copolymer of acrylic acid and methyl acrylate (AA / MA) , Copolymers of methyl acrylate and isobutylene (MA / IB), and copolymers of methyl acrylate and acrylic acid and vinyl acetate, but are not limited thereto.

 The acrylic acid polymer according to the present invention has an effect of increasing the durability of the separator membrane by making the silica structure harder than the above-mentioned effect.

In the present invention, such a C ₆ to C ₃₆ fatty acid, acrylic acid-based polymer or oxidized wax is referred to as a binder.

On the other hand, the inorganic particles are characterized by being in a form containing an active site. The active site is not limited as long as it can form a cross-linking structure with the C ₆ -C ₃₆ fatty acid or the oxidized wax, and specifically includes -COO, -NH ₂ , -CONH ₂ , -PO ₃ H ₂ , - A hydrophilic group consisting of SH, -SO ₃ H, -SO ₂ H, -NO ₂ , and -O (CH ₂ CH ₂ O) _n H (wherein n is an integer of 0 to 5) and a C ₃ to C ₃₀ alkyl group And a hydrophobic group consisting of C ₃ to C ₃₀ aryl groups. The active site according to an embodiment of the present invention is preferably -OH group, but is not limited thereto.

The method of forming the active sites of the inorganic particles can be performed by a conventional method such as an acid plasma treatment.

INDUSTRIAL APPLICABILITY The organic-inorganic porous separator according to the present invention can be prepared by controlling the composition of the C ₆ -C ₃₆ fatty acid, acrylic acid polymer or oxide wax, which serves as the content of the inorganic particles and the binder polymer, The pore structure of the active layer can be formed together with the pores, and the pore size and porosity can be controlled together.

Specifically, the organic binder polymer mixture preferably contains 1 to 200 parts by weight of a C ₆ to C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax used as a binder polymer with respect to 100 parts by weight of the inorganic particles. The pore size and porosity can be variously controlled while maintaining excellent cell membrane characteristics within the above range. If the amount is less than 1 part by weight, the content of the organic binder polymer is too small, so that the mechanical properties of the final organic / inorganic composite porous separator may be deteriorated due to the weakening of adhesion between the inorganic particles. If the amount is more than 200 parts by weight, The pore size and porosity due to the reduction of space may be reduced, resulting in a deterioration of final cell performance.

Fatty acid monoglyceride, fatty acid monopolyhydroxy alcoholide, and polymerized fatty acid monopolyhydroxy alcoholide may be selected to modify the active site of the inorganic particles with the above-mentioned C ₆ -C ₃₆ fatty acid-containing compound, But is not limited thereto. Since the organic binder polymer mixture according to the present invention contains the C ₆ to C ₃₆ fatty acid, the low melting point, the internal plasticity and the adhesion to the polyolefin substrate are improved

The oxidized wax preferably has a molecular weight (Mw) in the range of 200 to 40,000 g / mol, and may be an oxidized wax obtained by oxidizing a polyolefin having a molecular weight (Mw) of 200 to 40,000 g / mol. It is not.

The C ₆ to C ₃₆ fatty acid or oxidized wax according to the present invention is preferably a binder containing two or more fatty acid groups as terminal groups. Containing two or more fatty acid groups forms a crosslinked structure with the active sites on the surface of the inorganic particles and plays a role of strengthening the bonding force between the inorganic particles.

The method for preparing the organic binder polymer mixture may be carried out by adding a binder such as the C ₆ -C ₃₆ fatty acid, the acrylic acid polymer or the oxidized wax to the inorganic particles containing the active site in a solvent such as acetone or alcohol. This reaction can be carried out in a solvent containing 1 to 20 wt% of the binder at a temperature of about room temperature to about 60 DEG C for 1 to 24 hours.

The organic / inorganic porous separator according to the present invention may further contain inorganic particles (B) in an amount of 1 to 20 parts by weight based on 100 parts by weight of the organic binder polymer mixture to further improve the lithium ion transferring ability and the piezoelectricity.

The inorganic particles (B) is _{SiO 2, Al 2 O 3,} TiO 2, SnO 2, CeO 2, ZrO 2, BaTiO 3, SrTiO 3, Y 2 O 3, MgO, NiO, CaO, which is selected from ZnO and SiC One or two or more. Other Fig BaTiO to compensate piezoelectricity _{(piexoelectricity) 3, Pb (Zr} , Ti) O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB (Mg 3 Nb 2 / _{3) O 3 -PbTiO 3 (PMN} -PT) hafnia (HfO 2) , or mixtures thereof, and the number of days, lithium phosphate (Li ₃ PO _4), lithium titanium phosphate _{(Li x Ti y (PO 4} ) 3, 0 <x <2, 0 <y <3 ), lithium aluminum titanium phosphate _{(Li x Al y Ti z (} PO 4) 3, 0 <x <2, 0 <y <1, 0 <z <3), 14Li 2 O- _{9Al 2 O 3 -38TiO 2 -39P 2} O 5 (LiAlTiP) x O y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO _3, such as 0 < x <2, 0 <y < 3), Li 3 .25Ge0.25P0.75S 4 as lithium germanium thiophosphate Mani Titanium _{(Li x Ge y P z S} w, 0 <x <4, 0 <y < 1, such as, (Li _x N _y , 0 <x <4, 0 <y <2) such as 0 <z <1, 0 <w <5, Li ₃ N and the like, Li ₃ PO ₄ -Li ₂ S- ₂ SiS ₂ based _{glass (Li x Si y S z} , 0 <x <3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 P 2 S 5 , including, such as Thermal glass may further include a _{(Li x P y S z,} 0 <x <3, 0 <y <3, 0 <z <7) or a mixture thereof. And halogen compounds, such as _{AlX 3, MgX 2, SnX 2} ( where, X is a halogen atom) in order to form a solid electrolyte interface even at the electrode surface during the charge and discharge reaction of the secondary battery to improve the cycle characteristics and high rate characteristics of the battery As shown in FIG.

Further, according to the present invention,

a) preparing an organic binder polymer mixture in which the active site of the inorganic particles is modified with a C ₆ -C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax,

b) acid treatment or plasma treatment of the porous polyolefin substrate and

c) forming an active layer by coating and drying a slurry containing the organic binder polymer mixture and solvent of a) on at least one surface of the porous polyolefin substrate treated with acid or plasma, and then forming an active layer; &Lt; / RTI &gt;

Hereinafter, each step of the method for producing an organic / inorganic porous separator will be described in detail.

First, a) is a step of preparing an inorganic binder polymer mixture in which the active sites of the inorganic particles are modified with a C ₆ -C ₃₆ fatty acid, an acrylate polymer or an oxidized wax, and the inorganic binder polymer mixture according to the present invention is an inorganic material A strong cross-linking structure is formed between the particles and the binder, and the inorganic particles and the binder are not separated from each other, so that the inorganic particles can be prevented from desorbing. The inorganic particles, C ₆ to C ₃₆ fatty acid, acrylic acid-based polymer or oxidized wax constituting the organic binder polymer mixture are as described above.

Next, step b) is an acid treatment or a plasma treatment of the porous polyolefin substrate. The plasma treatment preferably uses a plasma output in the range of 10 to 1000 W in an atmosphere of nitrogen, oxygen, air, argon or a mixture thereof. The acid treatment is preferably conducted using water or alcohol adjusted to pH 1 to 3. The acid treatment and the plasma treatment are as described above.

Finally, in the step c), a slurry containing the organic binder polymer mixture of the step a) and a solvent is applied to at least one surface of the acid-treated or plasma-treated porous polyolefin substrate and dried to form an active layer.

At this time, the solvent of the slurry in the step c) may dissolve a C ₆ -C ₃₆ fatty acid, an acrylate polymer or an oxidized wax, and may contain 10 to 1000 parts by weight based on 100 parts by weight of the organic binder polymer mixture.

In step c), a slurry containing a solvent is prepared in the organic binder polymer mixture prepared in step (a), and the slurry is coated on the porous polyolefin substrate subjected to the acid treatment or plasma treatment. The coating method includes dip coating, die coating, roll coating , Comma coating, or a mixing method thereof, and the coated porous polyolefin substrate may be dried to produce an organic porous separator having an active layer formed thereon.

The drying method can be carried out by heat or ultraviolet irradiation, and a chemical crosslinking reaction may be caused to occur during drying, including a crosslinking agent. The drying method can be carried out by a conventional method.

The thickness of the active layer after drying in step c) is preferably 0.1 to 100 탆. And excellent membrane characteristics can be realized within the above range. The porosity and porosity can be freely controlled by adjusting the thickness of the active layer, the size of the inorganic particles, and the content of the binder, and the porosity and the pore size can be controlled within the range of 10 to 95% But are not necessarily limited thereto.

The slurry can be prepared by adding a solvent to the organic binder polymer mixture and using a mixer, a dispersing machine, etc. at a temperature ranging from room temperature to 60 ° C. The slurry according to the present invention can be produced in the form of a slurry in which inorganic particles are uniformly dispersed without requiring a separate dispersant and a dispersing step. Since the organic binder is chemically bonded to the inorganic particles, It seems to be possible to maintain the form.

The solvent used in the slurry dissolves a C ₆ to C ₃₆ fatty acid, an acrylate polymer or an oxidized wax. The active site of the porous polyolefin base and the inorganic particles must have a non-solvent property. Examples of such solvents include acetone, Tetrahydrofuran, acetonitrile, dimethylformamide, dimethylsulfoxide, diethylacetamide, N-methylpyrrolidone, and water. These solvents may be used in combination of two or more thereof.

Also, the solvent may include 10 to 1000 parts by weight based on 100 parts by weight of the organic binder polymer mixture, and a suitable slurry viscosity and an appropriate coating layer may be formed within the above range.

Conventional organic and inorganic porous separators have the advantage of excellent stability when applied to lithium ion batteries. However, when a lithium ion battery is stored at a high temperature for a long time, the moisture that was present during the production of the lithium ion battery increases the resistance The performance is deteriorated due to the reasons such as the above. In particular, since the inorganic material forming the separation membrane is hydrophilic, the water is strongly adsorbed chemically, resulting in degradation of long-term storage performance. However, since the inorganic porous particles according to the present invention are modified with a C ₆ -C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax to suppress side reactions between water and an electrolyte and are strongly adhered to the polyolefin substrate, , Thermal stability and electrolytic solution wettability, as well as excellent durability and high-temperature storage performance.

The slurry may further comprise an additive. As the additive, an additive having a functional group reactive with the OH group is used.

Further, the additive may have a functional group selected from at least one of phosphonate or phosphate (P = O), posiphonic acid (POH), silane (SiOR) and carboxylic acid (COOH).

Preferably, the additive is selected from the group consisting of dimethyl dimethoxy silane, dimethyl diethoxy silane, methyl trimethoxy silane, vinyl trimethoxy silane, phenyl Silanes such as phenyl trimethoxy silane and tetraethoxy silane, phosphonic acids such as phenyl phosphonic acid and methyl phosphonic acid, Phosphonates such as triphenyl phosphate and diemthyl methyl phosphonate, carboxylic acid esters such as octanoic acid, gallic acid and aminobenzoic acid, carboxylic acid).

When the additive is added in an amount of less than 0.1 wt%, the improvement of the long-term storage performance hardly occurs, and when the additive is added in an amount exceeding 3 wt%, there is no difference in performance from 0.1 wt% to 3 wt%. Therefore, the additive is preferably added in the range of 0.1 to 3 wt%.

The organic / inorganic porous separator according to the present invention can be used as a separator of an electrochemical device, preferably a lithium secondary battery. Particularly, when a gelable polymer is used as a component of the active layer, the electrolyte is polymerized by injecting an electrolyte after the battery is assembled using the separator, thereby forming a gel-type organic composite electrolyte.

The gel type organic / inorganic composite electrolyte of the present invention is easier to manufacture than the gel type polymer electrolyte of the prior art, and has a high ion conductivity and electrolyte impregnation rate due to a large number of spaces filled with the liquid electrolyte injected due to the microporous structure The battery performance can be improved.

At this time, when the organic / inorganic porous separator of the present invention is used as a separation membrane of an electrochemical device, preferably a lithium secondary battery, lithium ions can be delivered not only through the separation membrane substrate but also through the porous active layer, In the case where an internal short circuit occurs, the above-described safety improvement effect can be exhibited.

The present invention also provides a secondary battery comprising an anode, a cathode, an organic / inorganic hybrid porous separator of the present invention interposed between the anode and the cathode, and an electrolyte. Lithium secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries, and the like.

The electrochemical device can be manufactured according to a conventional method known in the art. For example, the electrochemical device is manufactured by interposing the electrode and the separator interposed therebetween, and then injecting an electrolyte into the assembly.

There is no particular limitation on the electrode to be used together with the organic / inorganic porous separator. However, the cathode active material may be a conventional cathode active material that can be used for a cathode of a conventional electrochemical device. Examples thereof include lithium manganese oxide, A lithium intercalation material such as a composite oxide formed by a lithiated cobalt oxide, a lithium nickel oxide, or a combination thereof, and the like. The negative electrode active material may be a conventional negative electrode active material that can be used for a negative electrode of a conventional electrochemical device. Examples of the negative electrode active material include lithium metal, lithium alloy and carbon, petroleum coke, Activated carbon, graphite or other lithium-absorbing materials such as carbon and the like. The positive electrode current collector may be a positive current collector, that is, a foil and a negative electrode current collector made of aluminum, nickel, or a combination thereof, that is, copper, gold, nickel or a copper alloy or a combination thereof And both electrodes are formed in such a manner that they are bonded to a foil produced by the above method.

An electrolytic solution used in the present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, and comprising an alkali metal cation or an ion composed of a combination thereof, such as K ^+, B ^- is PF ₆ ^{- _{, BF 4 -, Cl -,}} Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2 ) ₃ ^- , or an ionic ion-containing salt such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate DMC), dipropyl carbonate (DPC), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N- N-methyl-2-pyrrolidone (NMP), ethylmethyl car- bonate it is preferably dissolved and dissociated in an organic solvent composed of gamma-butanoate (EMC), gamma-butyrolactone (GBL), or a mixture thereof.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

The process of applying the organic or inorganic porous separator according to the present invention to a battery can be a lamination and folding process of a separation membrane and an electrode in addition to a general winding process.

When the organic porous separator according to the present invention is applied to the lamination process, it can be easily assembled due to excellent adhesive properties of C ₆ -C ₃₆ fatty acid, acrylic acid polymer or oxidized wax in the active layer. At this time, the adhesive force characteristics can be controlled by the inorganic particles and the binder content as main components or the physical properties of the polymer.

Hereinafter, preferred embodiments will be described in order to facilitate understanding of the present invention. However, the following examples are illustrative of the present invention, and the scope of the present invention is not limited to the following examples.

[Example 1]

1. Manufacture of organic binder polymer mixture

100 parts by weight of C ₁₆ fatty acid monoglyceride prepared in a concentration of 20% (w / w) in acetone was added to 100 parts by weight of SiO ₂ powder having an average particle diameter of 2 nm and -OH active site formed therein, To prepare an organic binder polymer mixture.

2. Plasma treatment of porous polyolefin substrates

In a nitrogen atmosphere, a plasma nozzle at a distance of about 50 mm from a polyethylene separator having a porosity of 40% and a thickness of 20 탆 was passed through the system at a speed of 10 m / min to form a system comprising a plasma nozzle and a generator (Plasma Trace, ) Was used to perform a plasma treatment at an intensity of 400 W

3. Manufacture of Porous Membrane

100 parts by weight of the organic binder polymer mixture was mixed with 300 parts by weight of a mixed solvent of acetone and tetrahydrofuran in a volume ratio of 1: 1 to prepare a slurry. The slurry thus prepared was coated on a plasma-treated polyethylene membrane by dip coating, and dried in an oven at 70 ° C for 30 seconds. The thickness of the coated active layer after drying was adjusted to 10 탆.

4. Measurement of ion conductivity

The separator prepared by the above method was immersed in an electrolytic solution and taken out again to measure the ion conductivity.

At this time, a lithium hexafluorophosphate salt was dissolved in a mixed solvent of ethylene carbonate / dimethyl carbonate (volume ratio 1: 1) at a concentration of 1M, and the electrolyte was used.

[Example 2]

Except that the oxidation wax having a molecular weight (Mw) of 1200 (g / mole) was used instead of the fatty acid monoglyceride of C _{16 in} the production of the organic binder polymer mixture, and the ionic conductivity Respectively.

[Example 3]

Except that polyacrylic acid having a molecular weight (Mw) of 3000 (g / mole) was used in place of fatty acid monoglyceride of C _{16 in} the production of an organic binder polymer mixture, and the ionic conductivity was measured Respectively.

[Comparative Example 1]

1. Preparation of Membrane

100 parts by weight of fatty acid monoglyceride, 100 parts by weight of SiO ₂ powder, 300 parts by weight of a mixed solvent of acetone and tetrahydrofuran in a volume ratio of 1: 1 were added and stirred to prepare a slurry. The slurry thus prepared was coated on a polyethylene separator having a porosity of 40% and a thickness of 20 탆 by a dip coating method and dried in an oven at 70 캜 for 30 seconds. The thickness of the coated active layer after drying was adjusted to 10 탆.

2. Ion conductivity measurement

The ionic conductivity of the separator prepared in Comparative Example 1 was measured by the method of Example 1.

The ion conductivity values of Examples 1 to 3 and Comparative Example 1 are shown in Table 1 below.

[Table 1]

Using the separators of Examples 1 to 3 and Comparative Example 1, a lithium secondary battery was fabricated as follows.

Manufacture of anode

88 wt% of LiCoO ₂ as a positive electrode active material, 6.5 wt% of carbon black as a conductive agent, and 5.5 wt% of PVdF as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to an aluminum thin film having a thickness of 20 탆 and dried to prepare a positive electrode, followed by roll pressing.

Cathode manufacturing

A negative electrode mixture slurry was prepared by adding 92 wt% of carbon powder, 6 wt% of PVdF as a binder and 2 wt% of carbon black as a negative active material to N-methyl-2-pyrrolidone (NMP) as a solvent. The positive electrode mixture slurry was applied to a copper thin film having a thickness of 20 탆 and dried to prepare a negative electrode, followed by roll pressing.

Manufacture of lithium secondary battery

Each of the positive electrode, the negative electrode, and the separators of Examples 1 and 2 and Comparative Example 1 was assembled using a stacking method, and 1 M of lithium hexafluorophosphate dissolved in ethylene carbonate: ethyl methyl carbonate = 1 : 2 (volume ratio) was injected to prepare a lithium secondary battery.

Each of the secondary batteries using the separators of Examples 1 to 3 and Comparative Example 1 thus manufactured was subjected to charge and discharge tests at a current density of 0.5 C in the range of 2.8 to 4.2 V. [ Specifically, the retention rate (%) obtained by measuring the capacity rate relative to the initial capacity obtained by 300 cycles of charging / discharging was measured, and the results are shown in Table 2 below.

[Table 2]

As described above, the organic / inorganic porous separator according to the present invention has improved ionic conductivity and charge / discharge retention by plasma-treated or acid-treated porous polyolefin substrate, It was confirmed that the porous polyolefin base material had better ion conduction characteristics and retention than Comparative Example 1 using the porous polyolefin base material.

Claims (15)

A porous polyolefin substrate which is subjected to a plasma treatment or an acid treatment and an active layer coated with an organic binder polymer mixture in which an active site of inorganic particles is modified with a C ₆ to C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax, Organic porous membrane. The method according to claim 1,
Wherein the organic binder polymer mixture comprises 1 to 200 parts by weight of a C ₆ to C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax with respect to 100 parts by weight of the inorganic particles. The method according to claim 1,
The inorganic particles are _{SiO 2, Al 2 O 3,} TiO 2, SnO 2, CeO 2, ZrO 2, BaTiO 3 , and Y one or more than one metal oxide, inorganic porous separator is selected from ₂ O _3. The method according to claim 1,
The active site is _{-COO, -NH 2, -CONH 2,} -PO 3 H 2, -SH, -SO 3 H, -SO 2 H, -NO 2, and _{-O (CH 2 CH 2 O)} n H (wherein, n is an integer of 0-5), a hydrophilic group and C ₃ ~ C ₃₀ alkyl group and C ₃ ~ one or more than one inorganic porous membrane consisting of a hydrophobic group selected from aryl (aryl) C ₃₀ of the composed. The method according to claim 1,
Wherein the C ₆ to C ₃₆ fatty acid or the oxidized wax contains two or more fatty acid groups as terminal groups as a binder. The method according to claim 1,
(AA / HAPS) of acrylic acid and 2-hydroxy-3-allyloxy-1-propanesulfonic acid, a copolymer of acrylic acid and methyl acrylate AA / MA), a copolymer of methyl acrylate and isobutylene (MA / IB), and a copolymer of methyl acrylate and acrylic acid and vinyl acetate. The method according to claim 1,
Further comprising inorganic particles (B) in an amount of 1 to 20 parts by weight based on 100 parts by weight of the organic binder polymer mixture. A secondary battery comprising the organic / inorganic porous separator according to any one of claims 1 to 7. a) preparing an organic binder polymer mixture in which the active site of the inorganic particles is modified with a C ₆ -C ₃₆ fatty acid, an acrylic acid polymer or an oxidized wax,
b) acid treatment or plasma treatment of the porous polyolefin substrate and
c) applying and drying a slurry containing the organic binder polymer mixture and solvent of the above a) on at least one side of the acid-treated or plasma-treated porous polyolefin substrate to form an active layer
Wherein the porous separator is a porous membrane. 10. The method of claim 9,
Wherein the plasma treatment in step b) uses a plasma output in the range of 10 to 1000 W in an atmosphere of nitrogen, oxygen, air, argon or a mixture thereof. 10. The method of claim 9,
Wherein the acid treatment of step (b) comprises using water or alcohol adjusted to a pH of 1 to 3. 10. The method of claim 9,
The solvent of the slurry of step c) may be a solvent of a porous organic / inorganic hybrid material containing 10 to 1000 parts by weight of C ₆ to C ₃₆ fatty acid, acrylic acid polymer or oxidized wax, based on 100 parts by weight of the organic binder polymer mixture Gt; 10. The method of claim 9,
Wherein the active layer in step (c) has a thickness of 0.1 to 100 탆 after drying. An organic or inorganic porous separator produced by the method of any one of claims 9 to 13. A secondary battery comprising the organic / inorganic porous separator of claim 14.