KR20160007147A - A porous membrane for secondary battery and preparation method thereof - Google Patents

Abstract

The present invention relates to a separation membrane for a secondary battery and a manufacturing method thereof. According to one embodiment of the present invention, the separation membrane includes a porous substrate, a primary inorganic particle coated on at least one surface of the porous substrate, a secondary inorganic particle coated on the coated primary inorganic particle, and a binder. The separation membrane can increase the safety of a battery.

Description

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

One embodiment of the present invention relates to a separation membrane for a secondary battery and a manufacturing method thereof.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified.

The electrochemical device is one of the most remarkable fields in this respect, and development of a rechargeable secondary battery has become a focus of attention. Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution .

Such a lithium secondary battery uses a polyolefin-based separator to prevent a short circuit between the positive electrode and the negative electrode. The separation membrane is typically subjected to a stretching process for controlling pore size and porosity for use as a separation membrane as well as using a polymer component melted at a temperature of 200 ° C or lower. When exposed to such a high temperature, heat shrinkage shrinking).

Therefore, when the battery rises to a high temperature due to internal / external stimulation, the possibility of short-circuiting between the positive electrode and the negative electrode due to shrinkage or melting of the separator, etc., There is a problem that it can ignite.

Korean Patent No. 10-0354948

An embodiment of the present invention has been made to solve the above problems, and it is an object of the present invention to provide a separation membrane for a secondary battery and a method of manufacturing the same, which can improve the safety of the battery.

According to an aspect of the present invention, there is provided a porous substrate comprising a porous substrate, a first inorganic particle coated on at least one side of the porous substrate, a second inorganic particle coated on the coated first inorganic particle, A separator comprising a binder is provided.

According to another embodiment of the present invention, there is provided a method of manufacturing a honeycomb structure including the steps of: (a) preparing a first inorganic particle, (b) preparing a first inorganic coating liquid containing the first inorganic particle and a binder, (c) (D) coating at least one surface of the porous substrate with the first inorganic coating liquid of (b), and (e) coating the coating layer coated with the first inorganic coating liquid on the first inorganic coating liquid. (C) with the second inorganic coating liquid.

In another embodiment of the present invention, there is provided an electrochemical device including the separator.

The separation membrane according to an embodiment of the present invention may include a first inorganic particle and a second inorganic particle, and the first inorganic particle may be coated such that the length (b) of the first inorganic particle faces the width direction (y) of the porous substrate . Accordingly, the separation membrane can have improved mechanical strength such as puncture strength, and can prevent the separation membrane from being stretched or shrunk.

In addition, by preventing stretching or shrinking of the separator, the anode and the cathode are short-circuited to prevent the battery from exploding or igniting, and the safety of the battery can be improved.

1 shows a first inorganic particle according to an embodiment of the present invention.
2 shows a separation membrane according to an embodiment of the present invention.
Fig. 3 is an enlarged view of the separation membrane of Fig.
4 shows a separator according to a comparative example.
5 is an enlarged view of the separation membrane of FIG.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Hereinafter, the present invention will be described in detail.

The separation membrane according to an embodiment of the present invention includes a porous substrate 100, first inorganic particles 121 coated on at least one surface of the porous substrate 100, The second inorganic particles 122 and the binder.

By including the first inorganic particles 121 and the second inorganic particles 122, the separation membrane can improve the mechanical strength such as puncture strength and prevent the separation membrane from being stretched or shrunk .

In addition, by preventing stretching or shrinking of the separator, the anode and the cathode are short-circuited to prevent the battery from exploding or igniting, and the safety of the battery can be improved.

The porous substrate 100 on which the first inorganic particles 121 and the second inorganic particles 122 are coated may be a porous substrate 100 generally used for an electrochemical device, For example, a polyolefin-based porous membrane or a nonwoven fabric. However, the present invention is not limited thereto.

Examples of the polyolefin-based porous film include polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polypentene, such as high-density polyethylene, linear low density polyethylene, low density polyethylene and ultra high molecular weight polyethylene, One membrane can be mentioned.

The nonwoven fabric may include, in addition to the polyolefin nonwoven fabric, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate ), Polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, and polyethylenenaphthalene are used alone or in combination. Or a nonwoven fabric formed of a polymer mixed with these. The structure of the nonwoven fabric may be a spun bond nonwoven fabric or a meltblown nonwoven fabric composed of long fibers.

The thickness of the porous substrate 100 is not particularly limited but may be in the range of 5 to 50 탆. The pore size and porosity present in the porous substrate 100 are also not particularly limited, but are 0.01 to 50 탆 and 10 to 95% Lt; / RTI >

The first inorganic particle 121 and the second inorganic particle 122 may be coated on the porous substrate 100 according to an embodiment of the present invention. The first inorganic particles 121 and the second inorganic particles 122 are not particularly limited as long as they are electrochemically stable. That is, the first inorganic particles 121 and the second inorganic particles 122 are oxidized and / or reduced at an operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ) It is not particularly limited. Particularly, when inorganic particles having ion transfer ability are used, the ion conductivity in the electrochemical device can be increased to improve the performance.

When inorganic particles having a high dielectric constant are used as the first inorganic particles 121 and the second inorganic particles 122, the dissociation of the electrolyte salt, for example, the lithium salt in the liquid electrolyte, is also enhanced to improve the ionic conductivity of the electrolyte .

For the reasons stated above, the first and second inorganic particles 121 and 122 may be inorganic particles having a dielectric constant of 5 or more, high-permittivity inorganic particles having a particle size of 10 or more, inorganic particles having lithium ion- And mixtures thereof.

Nonlimiting examples of the inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr _x , Ti 1 _-x ) O ₃ (PZT, where 0 <x <1), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, where, 0 <x <1, 0 <y <1), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 - x PbTiO 3 (PMN-PT, where 0 <x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ May be used alone or in combination of two or more.

In particular, the above-described _{BaTiO 3, Pb (Zr x Ti} 1 -x) O 3 (PZT, where 0 <x <1), Pb 1 - x La x Zr 1 -y Ti y O 3 (PLZT, where 0 < x <1, 0 <y < 1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 - x PbTiO 3 (PMN-PT, where 0 <x <1), hafnia ( HfO ₂ ) can exhibit a high dielectric constant characteristic with a dielectric constant of 100 or more. In addition, when a certain pressure is applied to the electrode, it is possible to generate a charge when the electrode is compressed or tensioned, so that a potential difference is generated between the electrodes, thereby preventing internal short- The safety of the device can be improved. Further, when the above-mentioned high-permittivity inorganic particles and inorganic particles having lithium ion transferring ability are mixed, their synergistic effect can be doubled.

The inorganic particle having the lithium ion transferring ability refers to an inorganic particle containing a lithium element but having a function of transferring lithium ions without storing lithium. The inorganic particles having lithium ion transferring ability can transfer and move lithium ions due to a kind of defect existing inside the particle structure, so that the lithium ion conductivity in the battery is improved and the battery performance is improved thereby .

Examples of the inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (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 as such (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate _{(Li x La y TiO 3,} 0 <x <2, 0 <y <3 ), Li _{3 .25} Ge _{0 .25} P _{0 .75} S ₄ Lithium, such as germanium Mani help thiophosphate lithium nitro, such as _{(Li x Ge y P z S} w, 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), Li 3 N fluoride _{(Li x N y, 0 <} x <4, 0 <y <2), Li 3 PO 4 -Li 2 SiS 2 , such as _{S-SiS 2 (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 (Li x P y S z, 0 <x <3, 0 <y <3, 0 <z , such as < 7) or mixtures thereof, and the like.

The first inorganic particles 121 including the inorganic particles may be coated on at least one surface of the porous substrate 100 and the first inorganic particles 121 may be in the form of a nano road .

The separator according to an embodiment of the present invention includes the first inorganic particles 121 in the form of nanorods, thereby improving mechanical strength such as puncture strength of the separator, Can be prevented. Further, it is possible to prevent a problem that the positive electrode and the negative electrode are short-circuited to cause the battery to explode or ignite, and the safety of the battery can be improved.

FIG. 1 shows a form of a first inorganic particle 121 according to an embodiment of the present invention. As shown in Fig. 1, when the diameter of the first inorganic particles 121 is a and the length is b, the aspect ratio (a: b) of the first inorganic particles 121 is 1: 2.5 to 1:10 have. The diameter of the first inorganic particles 121 having the aspect ratio of the above range may be 1 to 20 占 퐉, and preferably 10 to 20 占 퐉. In addition, the length of the first inorganic particles 121 may be 50 to 150 mu m.

When the aspect ratio of the first inorganic particles 121 is in the above-mentioned range, a nano rod shape can be obtained. In addition, the mechanical strength of the separation membrane containing the first inorganic particles 121 can be improved, and the separation or shrinkage of the separation membrane can be prevented.

FIG. 2 shows a separation membrane according to an embodiment of the present invention, and FIG. 3 shows an enlarged view of the separation membrane of FIG. 2, when the width direction y of the porous substrate 100 coincides with the vertical direction TD, the length direction (b) of the first inorganic particles 121 is smaller than the length direction b of the porous substrate 100 In the width direction (y).

The length direction b of the first inorganic particles 121 is coated toward the width direction y of the porous substrate 100 to prevent the separator from stretching or shrinking due to heat and pressure during the lamination process. can do.

The first inorganic particles 121 may be coated on the porous substrate 100 and then the second inorganic particles 122 may be coated on the coating layer coated with the first inorganic particles 121. [

The second inorganic particles 122 may be in the form of a circle and may form interstitial volumes between particles to form micropores. The pores may affect the ion exchange performance of the separator by the area through which the ions pass.

The first inorganic particles 121 and the second inorganic particles 122 may exist in a closely packed structure in a state of being substantially in contact with each other and the first inorganic particles 121 and the second inorganic particles 122 may be in contact with each other, The interstitial volume generated in the state of being separated can be the pore of the separation membrane.

As described above, the pore size formed by the first inorganic particles 121 and the second inorganic particles 122 may be 0.01 to 10 탆, and the porosity may be within the range of 5 to 95% It is not.

The average particle diameter of the second inorganic particles 122 may preferably be in the range of 0.01 to 10 mu m for the formation of a coating layer having a uniform thickness and a suitable porosity. If it is less than 0.01 탆, the dispersibility may be lowered, and it may be difficult to control the physical properties of the layer coated with the first inorganic particles 121 and the second inorganic particles 122. If the thickness is more than 10 μm, the thickness of the layer coated with the second inorganic particles 122 may increase to deteriorate the mechanical properties. If the pore size is excessively large, an internal short circuit may occur during charging and discharging of the battery Can be increased.

The first inorganic particles 121 and the second inorganic particles 122 may be coated on the porous substrate 100 at a weight ratio of 60:40 to 90:10 and preferably 80:20.

When the first inorganic particles 121 are contained in an amount exceeding the above range, the content of the second inorganic material becomes relatively small, and the contact area of the second inorganic material is reduced, thereby reducing the area of the pores. Also, as the pore decreases, the area through which the ions pass is decreased, so that the ion exchange performance of the separation membrane may be decreased.

If the amount of the first inorganic particles 121 is too small or less than the above range, the content of the second inorganic material may be relatively large. In such a case, it may be difficult to improve the mechanical strength to a desired level, and elongation or contraction of the separator may occur, and the anode and the cathode may be short-circuited. Further, a problem such as explosion or ignition of the battery may occur.

The thickness of the coating layer coated with the first inorganic particles 121 and the second inorganic particles 122 is not particularly limited, but may be adjusted in consideration of battery performance. However, in order to reduce the internal resistance of the battery, the thickness of the layer coated with the first inorganic particles 121 and the second inorganic particles 122 may be controlled within a range of 1 to 50 mu m, preferably 10 to 50 mu m Lt; / RTI &gt;

The separation membrane according to one aspect of the present invention may include a binder together with the first inorganic particles 121 and the second inorganic particles 122. The binder serves to connect and stably fix the first inorganic particles 121 and the second inorganic particles 122 so that the first inorganic particles 121 and the second inorganic particles 122, It is possible to prevent deterioration of the mechanical properties of the separation membrane coated with the catalyst.

As the binder, a polymer commonly used in the art can be used. In particular, a polymer having a glass transition temperature (Tg) of -200 to 200 ° C can be used because it can improve the mechanical properties such as the flexibility and elasticity of the finally formed separation membrane.

In addition, although the binder does not necessarily have ion conductivity, the performance of the electrochemical device can be further improved by using a polymer having ion conductivity. Therefore, a binder having a high permittivity constant can be used. Actually, the dissociation degree of the salt in the electrolytic solution depends on the permittivity constant of the solvent of the electrolyte. Therefore, the higher the permittivity constant of the polymer, the better the salt dissociation degree in the electrolyte. The permittivity constant of such a binder may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), in particular, 10 or more.

In addition to the functions described above, the binder may be characterized by being capable of exhibiting a high degree of swelling of the electrolyte by gelation upon impregnation with a liquid electrolyte. Accordingly, the solubility parameter of the binder is from 15 to 45 MPa ^1/2 or 15 to 25 MPa ^1/2, and 30 to 45 MPa ^1/2 range. Therefore, hydrophilic polymers having many polar groups can be used more than hydrophobic polymers such as polyolefins. If the solubility is more than 15 MPa ^1/2 and less than 45 MPa ^1/2, because it can be difficult to swell (swelling) by conventional liquid electrolyte batteries.

Non-limiting examples of the binder include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-trichlorethylene, polymethylmethacrylate ), Polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide but are not limited to, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, Nonethyl polyvinyl alcohol

and may include cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose. If the binder is commonly used, Can be used without.

In the separator, the binder may adhere the first inorganic particles 121 and the second inorganic particles 122 to each other so that the first inorganic particles 121 and the second inorganic particles 122 are bonded to each other 122 are connected and fixed). In addition, the first inorganic particles 121 and the second inorganic particles 122 can be kept bound to the porous substrate 100 by the binder.

The composition ratio of the first inorganic particles 121 or the second inorganic particles 122 and the binder is not particularly limited but is adjustable within a range of 5:95 to 99: 1 wt.%, Particularly 50:50 to 99: 1 Weight% is preferred. If the amount of the binder is less than 5: 95% by weight, the content of the binder becomes excessively large, thereby decreasing the pore size and porosity due to the reduction of the void space formed between the inorganic particles, The mechanical properties of the separator produced due to the weakening of the adhesion between the inorganic particles may be deteriorated because the binder content is too small.

The separation membrane according to an embodiment of the present invention may further include other additives in addition to the first inorganic particles 121, the second inorganic particles 122, and the binder.

The additive is not particularly limited as long as it is a substance required or additionally required for the operation or performance improvement of the electrochemical device and is continuously consumed due to consumption in the operation process.

Non-limiting examples of such an electrochemical device performance improving additive may include any one of additives for forming a solid electrolyte interface, a cell side reaction inhibiting additive, a thermal stability improving additive, an overcharge suppressing additive, or a mixture of two or more thereof .

As the additive for forming the solid electrolyte interface, any one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, cyclic sulfite, saturated sulphone, unsaturated sulphone, acyclic sulphone, Mixtures of two or more of these may be used, but are not limited thereto.

Examples of the cyclic sulfite include ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethylethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, Diethyl propyl sulfite, 4,6-diethyl propyl sulfite, and 1,3-butylene glycol sulfite, and the saturated sulphone includes 1 Propane sultone, and 1,4-butane sultone. Examples of the unsaturated sultone include ethene sultone, 1,3-propene sultone, 1,4-butene sultone, 1-methyl- Sulfone, and the like. Examples of the non-cyclic sulfone include divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone.

Examples of the cell side reaction inhibiting additive include ethylenediaminetetraacetic acid, tetramethylethylenediamine, pyridine, dipyridyl, ethylbis (diphenylphosphine), butyronitrile, succinonitrile, iodine, And derivatives thereof, or a mixture of two or more thereof, may be used, but are not limited thereto.

Examples of the thermostability-improving additive include one or two or more selected from the group consisting of hexamethyldisiloxane, hexamethoxycyclotriphosphazene, hexamethylphosphoramide, cyclohexylbenzene, biphenyl, dimethylpyrrole, and derivatives thereof But are not limited thereto.

The overcharge suppression additive may be, but is not limited to, a mixture of one or more selected from the group consisting of n-butylferrocene, a halogen-substituted benzene derivative, cyclohexylbenzene, and biphenyl.

Examples of the additives for improving the performance of the electrochemical device include derivatives in which at least one hydrogen atom bonded to the carbon atom of each compound is substituted with a halogen.

The content of the electrochemical device performance improving additive is 2 to 20 parts by weight, or 4 to 18 parts by weight, or 6 to 20 parts by weight, based on 100 parts by weight of the total amount of the first inorganic particles 121, the second inorganic particles 122, 15 parts by weight. When the content of the additive satisfies the above range, the effect of the addition is sufficiently exhibited, the excessive additive is released to prevent the side reaction, and the cycle of the battery can be prevented from being degenerated early.

In another embodiment of the present invention, a separation membrane production method is provided.

(B) preparing a first inorganic coating liquid containing the first inorganic particles (121) and a binder; (c) forming a first inorganic particle coating liquid containing a first inorganic particle and a second inorganic particle; (D) coating at least one surface of the porous substrate (100) with the first inorganic coating liquid of (b); and (e) coating the first inorganic coating liquid 1 &lt; / RTI &gt; inorganic coating liquid of (c) on a coating layer coated with an inorganic coating liquid.

The first inorganic particles 121 may be prepared by adjusting the shape and size of the first inorganic particles 121 by adjusting the temperature and time. For example, inorganic particles may be added to a solvent, followed by stirring at a temperature of 100 to 200 DEG C for 3 to 24 hours. When the inorganic particles have reached the desired size, the stirring can be stopped and the solvent can be removed to produce the first inorganic particles 121.

The solvent may be selected from the group consisting of acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, pyrrolidone, NMP), cyclohexane, water or mixtures thereof.

If the stirring temperature is 100 ° C or less and the temperature is too low, the inorganic particles may grow so that the inorganic particles may be difficult to grow because the temperature is too low, and the growth rate of the inorganic particles may be too slow, have. In addition, if the temperature is higher than 200 ° C, the growth rate of the inorganic particles may be too high to control the reaction rate, and it may be difficult to produce inorganic particles of desired size.

When the agitation time is within 3 hours, the first inorganic particles 121 may not be sufficiently formed, and when the agitation time exceeds 24 hours, the first inorganic particles 121 may grow to a desired size or larger.

The first inorganic particles 121 produced by the above-described method can be mixed with a binder to prepare a first inorganic coating liquid (step (b)). More specifically, after the binder is dissolved in a solvent to prepare a binder solution, the first inorganic particles 121 may be mixed with the binder solution to prepare a first inorganic coating liquid.

As the solvent, a solvent having a similar solubility index to a binder to be used and a low boiling point may be used. This is because the mixing can be made uniform and then the solvent can be easily removed.

Non-limiting examples of the solvent include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (N -methyl-2-pyrrolidone, NMP), cyclohexane, water or mixtures thereof.

The first inorganic particle 121 and optionally other additives may be added to the binder solution in which the binder and the solvent are mixed to prepare the first inorganic coating liquid.

Further, the second inorganic coating liquid can be produced similarly to the first inorganic coating liquid (step (c)). The second inorganic particle 122 and optionally other additives may be added to the above-mentioned binder solution to prepare the second inorganic coating liquid.

After the first inorganic coating liquid and the second inorganic coating liquid are prepared, the first inorganic coating liquid may be coated on at least one surface of the porous substrate 100 (step (d)).

Coating the first inorganic coating liquid, and then drying the first inorganic coating liquid.

After the step (d), the second inorganic coating liquid may be coated on the coating layer coated with the first inorganic coating liquid (step (e)).

The first inorganic particles 121 and the second inorganic particles 122 may be coated on the porous substrate 100 at a weight ratio of 60:40 to 90:10 and preferably 80:20.

When the first inorganic particles 121 are contained in an amount exceeding the above range, the content of the second inorganic material becomes relatively small, and the contact area of the second inorganic material is reduced, thereby reducing the area of the pores. Also, as the pore decreases, the area through which the ions pass is decreased, so that the ion exchange performance of the separation membrane may be decreased.

If the amount of the first inorganic particles 121 is too small or less than the above range, the content of the second inorganic material may be relatively large. In such a case, it may be difficult to improve the mechanical strength to a desired level, and elongation or contraction of the separator may occur, and the anode and the cathode may be short-circuited. Further, a problem such as explosion or ignition of the battery may occur.

The thickness of the coating layer coated with the first inorganic particles 121 and the second inorganic particles 122 is not particularly limited, but may be adjusted in consideration of battery performance. However, in order to reduce the internal resistance of the battery, the thickness of the layer coated with the first inorganic particles 121 and the second inorganic particles 122 may be adjusted within the range of 0.1 to 100 탆.

The first inorganic coating liquid and the second inorganic coating liquid may be coated on the porous substrate 100 by a conventional coating method known in the art. For example, a dip coating, a die coating, A roll coating, a comma coating, a mixing method thereof, or the like. In addition, the first inorganic coating liquid and the second inorganic coating liquid may be selectively formed on both or only one side of the porous substrate 100.

When a solvent is added to the first inorganic coating liquid and the second inorganic coating liquid, it is needless to say that the drying process of the coating layer is further required. Drying conditions can be batchwise or continuously dried using an oven or a heated chamber at a temperature range that takes into account the vapor pressure of the solvent used.

The separation membrane manufactured according to one embodiment of the present invention may be useful as a separation membrane of an electrochemical device, that is, a separation membrane interposed between an anode and a cathode.

The electrochemical device according to another embodiment of the present invention includes all devices that perform an electrochemical reaction, and specific examples thereof include all types of primary, secondary, fuel cell, solar cell, or supercapacitor devices Capacitors, and the like. In particular, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery may be included in the secondary battery.

The electrode to be applied together with the separator according to an embodiment of the present invention is not particularly limited and the electrode active material may be bound to an electrode current collector according to a conventional method known in the art.

Examples of the cathode active material include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof A lithium complex oxide may be used.

As a non-limiting example of the negative electrode active material, a conventional negative electrode active material that can be used for a negative electrode of an electrochemical device can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium adsorbing materials such as graphite or other carbon-based materials and the like can be used.

Non-limiting examples of the positive current collector include aluminum, nickel, or a combination thereof. Examples of the negative current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

The electrolytic solution which can be used in the electrochemical device according to an embodiment of the present invention is A ⁺

B ^- a salt of a structure, such as, A ⁺ is Li ^+, Na ^+, include alkali metal cation or an ion composed of a combination thereof, such as K ^+, and B ^- is _{^{PF 6 -, BF 4 -,}} Cl -, Br _{^{-, I -, ClO 4 -}} , AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2) 3 - and the anion thereof, such as (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethylsulfoxide, acetonitrile, dimethoxybenzene, and the like. An organic solvent composed of ethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone (g-butyrolactone) Dissolve or dissociate, but are not limited thereto.

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.

As a process for applying a separator according to an aspect of the present invention to a battery, a lamination, stacking and folding process of a separator and an electrode can be performed in addition to a conventional winding process.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

[Example 1]

1-1. Manufacture of anode

LiCoO ₂ was used as a positive electrode active material, and N-methyl-2-pyrrolidone (NMP) as a solvent was added to 95 wt% of LiCoO ₂ , 2.5 wt% of Super-P A positive electrode mixture slurry was prepared and then coated, dried and pressed on a long sheet type aluminum foil to prepare a positive electrode.

1-2. Cathode manufacturing

Artificial graphite was used as the negative electrode active material, and an anode mixture slurry was prepared by adding 95 wt% of artificial graphite, 2.5 wt% of Super-P (conductive agent) and 2.5 wt% of PVDF (binder) The negative electrode was prepared by coating, drying and pressing on a sheet-like copper foil.

1-3. Preparation of Membrane

The BaTiO ₃ powder was added to NMP, stirred at a temperature of 150 ° C for 8 hours, and dried to prepare a first inorganic particle 121 having a diameter of 20 μm and a length of 80 μm.

The first inorganic particles 121 were dispersed in a polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) binder solution to obtain a first inorganic particle 121 (BaTiO ₃ / PVdF-HFP = 90/10 An inorganic coating liquid was prepared.

Further, Al ₂ O ₃ powder was dispersed in a binder solution of polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) to prepare a (Al ₂ O ₃ / PVdF-HFP = 90/10 (weight% 2 inorganic coating liquid was prepared.

After the first inorganic coating liquid was coated on the porous polyethylene membrane, the second inorganic coating liquid was coated on the coating layer coated with the first inorganic coating liquid.

The first inorganic particles 121 and the second inorganic particles 122 were coated at a weight ratio of 80:20 and the coating thickness of the first inorganic particles 121 and the second inorganic particles 122 was 15 μm.

1-4. Manufacture of batteries

The separators 1-3 were sandwiched between the positive and negative electrodes of 1-1 and 1-2 described above and assembled using a stacking method. 1M lithium hexafluorophosphate (LiPF ₆ ) was added to the assembled battery The dissolved ethylene carbonate / propylene carbonate / diethyl &lt; RTI ID = 0.0 &gt;

Carbonate (EC / PC / DEC = 30: 20: 50% by weight) electrolyte was injected to prepare a lithium secondary battery.

[Comparative Example 1]

(Al ₂ O ₃ / PVdF-HFP = 90/10 (% by weight)) after dispersing Al ₂ O ₃ powder in a polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) binder solution, ) Was coated on a porous polyethylene film to prepare a separation membrane, a lithium secondary battery was produced in the same manner as in Example 1.

The structure of the separation membrane used in Comparative Example 1 is shown in FIG. 4 and FIG.

[Experimental Example 1]

Table 1 shows the number of batteries that were ignited by charging 30 batteries manufactured in Example 1 and 30 batteries manufactured in Comparative Example 1 to 4.2 V, respectively, after the impact test. The impact test proceeded by dropping a 9.1 kg metal bar of 15.8 mm length from a height of 61 cm to the center of the cell.

Example 1 Comparative Example 1 Number of ignited cells One 15 The firing rate of the battery 3.3% 50%

As shown in the above Table 1, as a result of the impact test, it was confirmed that the battery of Example 1 was greatly reduced in the number of batteries ignited as compared with the battery of Comparative Example 1, and thus the ignition rate was greatly reduced.

It can be seen that the application of the separator according to an embodiment of the present invention to the battery improves the mechanical strength of the battery and prevents the separation membrane from being stretched or shrunk. As a result, the problem of explosion or ignition of the battery is reduced, and the safety of the battery is improved.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

100: Porous substrate
110: inorganic particles
121: First inorganic particle
122: second inorganic particle

Claims (16)

Porous substrates,
A first inorganic particle coated on at least one surface of the porous substrate,
A second inorganic particle coated on the coated first inorganic particle and
A separator comprising a binder.
The method according to claim 1,
Wherein the porous substrate comprises a polyolefin-based porous membrane or a nonwoven fabric.
The method according to claim 1,
Wherein the first inorganic particles and the second inorganic particles include one or more selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transporting ability, and mixtures thereof. .
The method of claim 3,
Inorganic particles is greater than or equal to the dielectric constant of 5, _{BaTiO 3, Pb (Zr x,} Ti 1 -x) O 3 (PZT, 0 <x <1), Pb 1 - x La x Zr 1 -y Ti y O 3 (PLZT , 0 <x <1, 0 <y <1), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 - x PbTiO 3 (PMN-PT, 0 <x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ And at least two kinds thereof.
The method of claim 3,
Wherein the inorganic particles having lithium ion transferring ability are 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), (LiAlTiP) x O y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , , 0 <y <1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 (Li x Si y S _{z, 0 <x <3,} 0 <y <2, 0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 <z &Lt; 7) -glass. &Lt; / RTI &gt;
The method according to claim 1,
Wherein the first inorganic particles are in the form of nanorods.
The method according to claim 1,
Wherein the aspect ratio (a: b) of the first inorganic particles is 1: 2.5 to 1:10 when the diameter of the first inorganic particles is a and the length is b.
The method according to claim 1,
When the width direction (y) of the porous substrate coincides with the vertical direction (MD)
(B) of the first inorganic particles is oriented in the width direction (y) of the porous substrate.
The method according to claim 1,
Wherein the second inorganic particles are in a circular shape.
The method according to claim 1,
And the average particle diameter of the second inorganic particles is 0.01 to 10 탆.
The method according to claim 1,
Wherein the weight ratio of the first inorganic particles to the second inorganic particles is 60:40 to 90:10.
The method according to claim 1,
Wherein the total thickness of the first inorganic particles and the second inorganic particles is 1 to 50 占 퐉.
The method of claim 12,
Wherein the total thickness of the first inorganic particles and the second inorganic particles is 10 to 50 占 퐉.
The method according to claim 1,
The binder may be selected from the group consisting of polyvinylidene fluoride-cohexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polybutyl acrylate polybutylene terephthalate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, Polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, and the like. ), City No ethyl cellulose (cyanoethylcellulose), cyanoethyl sucrose (cyanoethylsucrose), pullulan (pullulan) and carboxymethyl cellulose (carboxyl methyl cellulose) membrane characterized in that it comprises one or two or more selected from the group consisting of.
(a) preparing a first inorganic particle,
(b) preparing a first inorganic coating liquid containing the first inorganic particles and a binder,
(c) preparing a second inorganic coating liquid comprising a second inorganic particle and a binder,
(d) coating at least one surface of the porous substrate with the first inorganic coating liquid of (b); and
(e) coating on the coating layer coated with the first inorganic coating liquid with the second inorganic coating liquid of (c).
An electrochemical device comprising the separation membrane of claim 1.

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