KR101636857B1 - Separator containing coating layer, manufacturing thereof and battery using the separator - Google Patents

Abstract

The present invention relates to a separation membrane including a coating layer, a method of manufacturing the same, and a battery using the same, and more particularly, to a separation membrane having improved peeling strength and heat shrinkage ratio of the separation membrane.
More particularly, the present invention relates to a polyolefin-based porous base film, and a coating layer containing a binder and inorganic particles formed on one or both sides of the base film, wherein the separating membrane including the organic / inorganic mixed coating layer has excellent peel strength And heat shrinkage ratio.

Description

TECHNICAL FIELD [0001] The present invention relates to a separation membrane including a coating layer, a method of manufacturing the same, and a battery using the same. BACKGROUND ART [0002]

The present invention relates to a separation membrane including a coating layer, a method for producing the same, and a battery using the same.

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

In recent years, electrochemical cells for increasing the portability of electronic devices have become lightweight and miniaturized, and at the same time, they are required to have excellent shape stability by heat for the production of high capacity batteries.

In particular, when a polyolefin-based material is used as a base film of a separation membrane, a means for solving the possibility of short-circuiting between the anode and the cathode due to shrinkage upon overheating and piercing the separation membrane may be used as a means for preventing a mixture of inorganic particles and a binder polymer on at least one surface of the polyolefin- An organic / inorganic composite separator having a porous active layer formed thereon was proposed

However, the separation membrane containing a coating layer containing an inorganic substance can improve the heat resistance, but the adhesion force with the electrode is lowered and the peeling force and the heat shrinkage rate of the base material are not greatly improved, There was a problem of poor stability.

In addition, the coating layer formed on the surface of the porous substrate lowers the air permeability of the separation membrane by blocking the pores on the surface, and greatly reduces the ion movement path between the anode and the cathode. As a result, the charging and discharging performance of the battery deteriorates .

Korean Patent No. 10-0727248 (published on June 11, 2007)

Accordingly, a problem to be solved by the present invention is to provide a separator having improved heat resistance of a separator by forming a coating layer containing an inorganic material and having excellent peel strength and heat shrinkage ratio without decreasing air permeability by controlling coating conditions, And a battery using the same.

According to an embodiment of the present invention, there is provided a separation membrane comprising a polyolefin-based porous base film and a coating layer containing a binder and inorganic particles formed on one or both sides of the base film, wherein the coating layer is peeled off from the polyolefin- And the heat shrinkage rate measured after leaving the separator at 150 DEG C for 1 hour is not more than 10% in the machine direction (MD) and the transverse direction (TD), respectively, Wherein the separation membrane has an air permeability of 150 to 300 sec / 100 cc.

According to another embodiment of the present invention, there is provided a process for producing a separator comprising a polyolefin-based porous substrate film and a coating layer containing a binder and inorganic particles on one or both sides of the substrate film, And a humidity of 13 g / m < ³ > or less.

According to another embodiment of the present invention, there is provided an electrochemical cell including a positive electrode, a negative electrode, and an electrolyte, and a separator interposed between the positive electrode and the negative electrode, wherein the separator is a separator , And an electrochemical cell.

The separation membrane according to the embodiments of the present invention has excellent heat resistance and a good separation force and heat shrinkage ratio without decreasing the air permeability of the separation membrane because a coating layer containing a binder and inorganic particles is formed on one side or both sides of the base film .

Further, the present invention shows the effect of improving the resistance to heat shrinkage of the separator, which is generated when the battery is overheated, by using the separator having excellent heat resistance and adhesion to the electrode, and providing a battery excellent in shape preservability and charge- .

FIG. 1 is a schematic view showing a separation membrane manufacturing method according to one embodiment of the present invention and another embodiment.
2 is a schematic view showing a surface of a coating layer of a separation membrane according to an embodiment of the present invention.
3 is a scanning electron microscope (SEM) photograph (400 times) of a surface of a coating layer of a separation membrane formed according to an embodiment of the present invention.
4 is a scanning electron microscope (400 times) photograph of the surface of a coating layer of a separation membrane formed according to a comparative example of the present invention.
5 shows a surface of a pattern bar according to an embodiment of the present invention.

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

The separation membrane according to an embodiment of the present invention includes a polyolefin-based porous base film and a coating layer containing a binder and inorganic particles formed on one or both sides of the base film.

The heat shrinkage of the coating layer measured on a polyolefin porous base material film is 50 gf / cm or more and the separator is left at 150 ° C. for 1 hour. The measured heat shrinkage is measured in the machine direction (MD) TD, and Transverse Direction) of 10% or less, respectively, and the permeability of the separator is 150 to 300 sec / 100 cc.

Specifically, the peeling force may be 100 gf / cm or more, the peeling force may be 200 gf / cm or more and / or the heat shrinkage may be 8% or less in the machine direction and the right angle direction respectively, / cm < / RTI > and / or the heat shrinkage may be less than or equal to 5% each in the machine direction and the perpendicular direction, and the peel force may be greater than or equal to 600 gf / cm and / or the heat shrinkage may be less than or equal to 4% have.

Accordingly, the separator according to an embodiment of the present invention has excellent peeling resistance of the coating layer, and can prevent the inorganic particles in the coating layer from being detached during assembly of the battery or the like, Is sufficiently strong so that shrinkage of the base film due to heat can be suppressed and separation between the coating layer and the base film, which may occur when the battery is overheated, can be prevented.

In addition, it has an excellent heat resistance and is capable of suppressing shrinkage of the base film, preventing short-circuiting of the electrode due to shrinkage, and being excellent in high-temperature safety.

The method of measuring the peeling force of the coating layer on the polyolefin-based porous base film is not particularly limited and a method commonly used in the technical field of the present invention can be used. The separation membrane containing the prepared coating layer is cut to a size of about 1.5 cm in width (MD) to about 7 cm in length (TD), and a transparent double-sided tape (3M), and then measuring the force required for peeling off the coating layer using a universal test machine (UTM).

The method of measuring the heat shrinkage percentage of the separation membrane is not particularly limited, and a method commonly used in the technical field of the present invention can be used. A non-limiting example of the method of measuring the heat shrinkage ratio is as follows: The prepared separation membrane is cut into a size of about 5 cm in width (MD) about 5 cm in length (TD) And then measuring the degree of shrinkage of the separator in the machine direction (MD) and the perpendicular direction (TD) to calculate the heat shrinkage ratio.

The air permeability of the separator may be 150 to 300 sec / 100 cc, and may be 200 to 250 sec / 100 cc. A non-limiting example of the method of measuring the air permeability is as follows: Ten specimens were cut at each of the four points, and a circular membrane having a diameter of 1 inch was passed through each of the specimens using an air permeability measuring device EG01-55-1MR (manufactured by Asahi Seiko Co., Ltd.) to transmit air of 100 cc The average time is measured five times each, and the average value is calculated to measure the air permeability.

Hereinafter, a separation membrane according to an embodiment of the present invention will be described in more detail.

Porous substrate film

The porous substrate film may be a polyolefin-based film. Examples of the porous substrate film include a polyethylene single film, a polypropylene single film, a polyethylene / polypropylene double film, a polypropylene / polyethylene / polypropylene triple film, and a polyethylene / polypropylene / A membrane selected from the group consisting of membranes can be used.

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

Non-limiting examples of the polyolefin resin include polyethylene (PE), polypropylene (PP), polybutylene (PB), polyisobutylene (PIB) Poly-4-methyl-1-pentene (PMP), and the like. These may be used alone or in combination of two or more. That is, the polyolefin-based resin may be used alone, or a copolymer or a mixture thereof may be used.

Non-limiting examples of the resin other than the polyolefin resin include polyamide (PA), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polychlorotrifluoroethylene , PCTFE), polyoxymethylene (POM), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVdF), polycarbonate (PC), polyarylate PAR), polysulfone (PSF), polyetherimide (PEI), and the like. These may be used alone or in combination of two or more.

Coating layer

The coating layer is a layer containing a binder and inorganic particles, and may be in contact with an electrode when applied to an electrochemical cell, and may be formed on one or both surfaces of the porous substrate film. The coating layer can improve the thermal stability of the separation membrane.

The thickness of one surface of the coating layer formed on the base film may be 0.1 to 10 탆, specifically 1 to 5 탆. It is possible to prevent the thickness of the entire separation membrane from becoming excessively thick within the above-mentioned thickness range, and to prevent the internal resistance of the battery from increasing. The method of measuring the thickness of the coating layer is not limited, but a non-limiting example can be measured using an SEM (Cross section) image and a micro-caliper.

end. bookbinder

The binder may be an organic binder, for example, an acrylic copolymer, polyvinylidenefluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride- trichlorethylene, PVDF-TCE, polyvinylidenefluoride-trifluoroethylene (PVDF-CTFE), polymethylmethacrylate (PMMA), polybutylacrylate PBA, Polyacrylonitrile PAN, polyvinylpyrrolidone (PVP), polyvinylacetatem (PVAc), polyvinyl alcohol (PVAl), polyethylene-co-vinylacetate , PEVA), polyethylene oxide (PEO), polyarylate (PAR), cellulose acetate cellulose acetate (CA), cellulose acetate butyrate (CAB), cellulose acetate propionate (CAP), cyanoethylpullulan (CYEPL), cyanoethylpolyvinylalcohol (CRV), cyanoethyl cellulose (CEC), cyanoethyl sucrose (CRU), pullulan, carboxyl methyl cellulose (CMC), polyimide ) And polyamic acid (PAA). The weight average molecular weights (Mw) of two or more kinds of binders contained in the coating layer may be the same or different.

The polyamic acid may have a weight average molecular weight (Mw) of from 20,000 to 100,000 g / mol, and more preferably from 30,000 to 90,000 g of the polyamic acid as a binder of the coating layer. / mol, and can be from 40,000 to 90,000 g / mol. When the molecular weight is in the above range, solubility in a low boiling point solvent is increased and heat resistance can be improved

The polyamic acid may be represented by the following formula (1) or (2).

[Chemical Formula 1]

(2)

In the above formula (1) or (2)

R ₁ , R ₅ , and R ₇ are each independently substituted or unsubstituted aromatic hydrocarbons having 6 to 30 carbon atoms; A substituted or unsubstituted aliphatic hydrocarbon having 2 to 20 carbon atoms; Or a substituted or unsubstituted alicyclic hydrocarbon having 3 to 24 carbon atoms. R ₁ , R ₅ , and R ₇ may be the same or different.

Specifically, the aromatic hydrocarbon having 6 to 30 carbon atoms may be represented by the following formula (3).

(3)

In Formula 3, Ar ₁ To Ar ₄ each independently can be an renil aryl having 6 to 15 unsubstituted or substituted, Ar ₁ to Ar ₄ are each can be different or equal to each other, X ₁ to X ₃ are independently a single bond, O together , C (= O) ₂ , C (= O) NH, unsubstituted or substituted C 1 -C 10 alkylene, specifically C 1 -C 4 alkylene, And may be a silylated ring. For example, the substituted alkylene or alkylene silica can be substituted once or twice by F, OH, CH _3, CF _3.

M, l and o may each independently be 0 or 1. Specifically, when m is 1 and l and o are 0, X ₂ And X ₃ is a single bond and Ar ₂ is a trivalent substituted or unsubstituted arylene having 6 to 15 carbon atoms, and when m and l are 1 and o is 0, X ₃ is a single bond and Ar ₃ May be a trivalent substituted or unsubstituted arylene having 6 to 15 carbon atoms. When all of m, l and o are 0, X ₁ To X ₃ is a single bond, Ar ₁ may be a tetravalent substituted or unsubstituted arylene having 6 to 15 carbon atoms, and may be, for example, a tetravalent substituted or unsubstituted phenyl or naphthyl.

(여기서, R₃ 및 R₄는 각각 독립적으로 탄소수 1 내지 5의 알킬렌일 수 있고, Ar₅는 치환되거나 비치환된 탄소수 6 내지 15의 아릴렌일 수 있다. Ar₅가 치환되는 경우, CH₃, OH, SH 또는 NH₂로 1회 내지 3회 치환될 수 있다.)일 수 있다. R₂, R₆, 및 R₈은 각각 동일하거나 상이할 수 있다.Wherein R ₂ , R ₆ , and R ₈ are independently selected from substituted or unsubstituted aromatic hydrocarbons having 6 to 30 carbon atoms; A substituted or unsubstituted aliphatic hydrocarbon having 2 to 20 carbon atoms; A substituted or unsubstituted alicyclic hydrocarbon having 3 to 24 carbon atoms; or

(Wherein, when R ₃ and R ₄ each independently can be alkyl renil having 1 to 5, Ar ₅ is a substituted or that beach may be a renil aryl having 6 to 15 ring. The Ar ₅ optionally substituted, CH _3, OH, SH or NH < ₂ >). R ₂ , R ₆ , and R ₈ may be the same or different.

Specifically, in R ₂ , R ₆ , and R ₈ , the substituted or unsubstituted aromatic hydrocarbon having 6 to 30 carbon atoms may be represented by the following formula (4).

[Chemical Formula 4]

In Formula 4, Ar ₆ And Ar ₉ may independently be arylene having 6 to 15 carbon atoms, Ar ₆ to Ar ₉ may be the same or different from each other, and X ₄ to X ₆ are each independently a single bond, O, S, C = O), S (= O) ₂ , C (= O) NH, unsubstituted or substituted C 1 -C 10 alkylene, specifically C 1 -C 4 alkylene, or substituted or unsubstituted silylene silylene). For example, the substituted alkylene or alkylene silica can be substituted once or twice by F, OH, CH _3, CF _3.

P, q and r may each independently be 0 or 1. P is 1, q and r are 0, X ₅ And X ₆ is a single bond, wherein Ar ₆ and Ar ₇ each independently may be substituted or unsubstituted phenyl or naphthyl. When p and q are 1 and r is 0, X ₆ may be a single bond. When p, q and r are all 0, X ₄ And X ₆ is a single bond, and Ar ₆ may be a divalent substituted or unsubstituted arylene having 6 to 15 carbon atoms.

In Formula 4, X ₄ may be in the ortho, meta, or para position with respect to the amine group (-NH-) of Formula 1 or Formula 2. May be specifically in the meta position, and the solubility can be improved if it is located at the meta position with respect to the amine group.

In Formula 1, n is an integer of 30 to 10000, an integer of 100 to 1000, an integer of 50 to 500, or an integer of 50 to 300.

In Formula 2, x may be an integer between 15 and 5000, y may be an integer between 15 and 5000, specifically, x may be an integer between 50 and 500, y may be an integer between 50 and 500, , More specifically, x may be an integer between 25 and 250, and y may be an integer between 25 and 250. [

Specifically, a polyamic acid represented by the following formula (5) may be used as a binder.

[Chemical Formula 5]

In the above formula, x and y may each be an integer between 15 and 5,000, and may be an integer between 50 and 500, for example, between 75 and 250.

The formula (5) includes an amic acid unit (x) containing at least one sulfone group but not a trifluoromethyl group, an amic acid unit (y) containing at least one sulfone group and at least one trifluoromethyl group, With a repeating structure, the ratio of x: y can be from 9: 1 to 5: 5. The polyamic acid within the above range is advantageous in that it exhibits a sufficiently high solubility for a low boiling point solvent, while it is not so high in solubility as to dissolve in an electrolytic solution or the like.

The separator according to another embodiment of the present invention may use two or more kinds of PVdF-HFP copolymers having different weight average molecular weights as a binder of the coating layer. The weight average molecular weight may be 500,000 g / mol or more, A PVdF-HFP copolymer less than 900,000 g / mol and a PVdF-HFP copolymer greater than 900,000 g / mol.

For example, a PVdF-HFP copolymer having a weight average molecular weight of less than 500,000 to less than 900,000 g / mol and a PVdF-HFP copolymer having a weight average molecular weight of 900,000 g / mol or more can be mixed at a weight ratio of 4: 5 to 6: 4 have. Within the above range, it is possible to produce a battery in which the electrolyte impregnability of the separator is excellent and the electric power output is efficiently produced, and the excellent strength and adhesion to the electrode can be ensured.

I. Inorganic particle

The inorganic particles in the coating layer coated on the porous substrate film serve as a kind of spacer capable of maintaining the physical form of the coating layer. Accordingly, even when the electrochemical device is overheated, heat shrinkage of the substrate can be suppressed, and an interstitial volume exists between the inorganic particles, so that micropores can be formed.

The kind of the inorganic particles contained in the coating layer is not particularly limited, and inorganic particles that are conventionally used in the art can be used. Non-limiting examples of the inorganic particles include Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ , Ga ₂ O ₃ , TiO _2, and SnO ₂ . These may be used alone or in combination of two or more. For example, Al ₂ O ₃ (alumina) can be used.

The size of the inorganic particles is not particularly limited, but may be an average particle diameter of 100 nm to 1000 nm, specifically 300 nm to 600 nm. In the case of using the inorganic particles having the above-mentioned size range, it is possible to prevent degradation of the dispersibility of the inorganic particles and the processability of the coating in the coating liquid, and the thickness of the coating layer can be appropriately controlled to prevent deterioration of mechanical properties and increase in electrical resistance .

In addition, there is an advantage that it is possible to reduce clogging of the pores generated in the separation membrane, thereby reducing the probability of occurrence of an internal short circuit during charging and discharging of the battery.

All. menstruum

In preparing the coating liquid for forming the coating layer of the separation membrane, the binder and the inorganic particles may be used in the form of a polymer solution and an inorganic dispersion in which the binder and the inorganic particles are dispersed in an appropriate solvent. The suitable solvent is not particularly limited, and solvents commonly used in the art may be used. As the above-mentioned suitable solvent, a high boiling point solvent may be used in addition to the low boiling point solvent.

Non-limiting examples of the low-boiling solvent include acetone, tetrahydrofuran (THF), etc. These solvents may be used alone or in admixture of two or more.

Non-limiting examples of the high-boiling solvent include dimethyl formamide DMF, dimethyl sulfoxide (DMSO), dimethylacetamide DMAc, dimethyl carbonate (DMC), or N N-methyl pyrrolidone (NMP), etc. These may be used alone or in combination of two or more.

For example, at least one solvent selected from the group consisting of acetone and DMAc can be used. In this case, the binder is sufficiently dissolved, the inorganic particles are sufficiently dispersed to facilitate the preparation of the coating liquid, So that the air permeability can be improved.

In this embodiment, the content of the inorganic dispersion relative to 100 parts by weight of the coating liquid may be adjusted so that the ratio of the binder to the inorganic particles in the coating layer is 50:50 to 10:90, specifically 30:70 to 5:95 have. Sufficient heat dissipation characteristics by the inorganic particles can be expected within the above range and the content of the organic binder can be appropriately adjusted to relatively secure the adhesion of the separation membrane to an appropriate level or higher and effectively suppress the heat shrinkage of the separation membrane.

Hereinafter, a method of manufacturing a separation membrane according to an embodiment of the present invention will be described with reference to FIG.

The method of manufacturing a separation membrane according to this embodiment may include forming a coating layer on a substrate film at an absolute humidity of 13 g / m ³ or less. Specifically, the absolute humidity may be 3 to 13 g / m ³ .

Under the absolute humidity of the above range, the phase separation phenomenon appearing on the surface during coating can be controlled to improve the peeling force with the substrate without lowering the air permeability. In addition, the effect of improving the shrinkage ratio can be maximized by increasing the peeling force of the coating layer on the polyolefin-based porous base film.

Absolute humidity means the amount of water vapor at the current temperature, and is the mass of steam in air of 1 m 3 in g, which can be calculated by the following equation (1).

[Formula 1]

Absolute humidity (g / m ³ ) = (Relative humidity x Saturated water vapor at current temperature) / 100

The relative humidity can be calculated by the following equation (2).

[Formula 2]

Relative humidity (%) = (water vapor amount at current temperature / saturated water vapor amount at current temperature) × 100

The method of measuring the absolute humidity is not particularly limited and may be carried out by a method conventionally measured in the art. For example, by using an absolute hygrometer (absorption hygrometer), water vapor in a certain air is absorbed into a hygroscopic agent, and the absolute humidity is directly measured according to the increase of the mass of the hygroscopic agent, or the relative humidity measured using a dry- It can be derived from Equations 1 and 2 using the saturated steam graph.

The method of controlling the absolute humidity is not particularly limited and can be performed by a method commonly used in the art. For example, the room temperature may be lowered to allow the water vapor to condense so that the absolute humidity is lowered or physically removed using a dehumidifier or other device.

Hereinafter, a method of manufacturing a separation membrane according to an embodiment of the present invention will be described in detail with reference to FIG.

Immersion  step

The base film 2 is moved from the base film supply section 1 to the bath 4 containing the coating liquid 5 using one or more rolls 3 to form a coating liquid 5, the base film 2 is immersed. At this time, the speed at which the base film 2 is moved from the base film supply part 1 to the bath 4 can be kept constant for uniform coating.

The base film (2) may be a polyolefin-based porous base film, and a method of forming fine pores in the base film is not particularly limited and can be generally used in the art. For example, the wet process can control the thickness of the separator thinly and uniformly compared to the dry process, uniformly regulate the size of the pores produced, and produce a porous separator having better mechanical strength.

There is no particular limitation on the method for producing the coating liquid (5), but it is also possible to prepare a coating liquid by preparing a polymer solution in which a binder is dissolved in a suitable solvent and an inorganic dispersion liquid in which inorganic particles are dispersed, can do.

Further, the polymer solution, the inorganic dispersion liquid and the solvent are mixed and then sufficiently stirred using a ball mill, a beads mill, a screw mixer or the like to prepare a coating solution in the form of a mixture can do.

 The substrate film 2 is immersed in the coating liquid 5 for a predetermined time and then pulled up using the roll 3. The surface of the base film 2 is coated with the thin coating liquid 5 while the base film 2 is pulled up. The pull-up speed can be constant for a uniform coating, and the velocity at this time can determine the thickness. The faster the speed, the thicker the coating layer.

Extra coating liquid removal step

Thereafter, a part of the coating liquid 5 may be removed to control the thickness of the coating layer or to flatten the surface of the coating layer so that the extra coating liquid 7 applied to the substrate film 2 does not flow. At this time, the excess coating liquid can be removed by using the wire bar 6 or the like.

Drying step

The coating liquid (5) applied on one side or both sides of the base film (2) in a solution state may be subjected to a step of removing the remaining solvent without being evaporated in the coating layer through a drying process under certain conditions.

The drying method is not particularly limited, but examples thereof include air blowing, IR heater, UV curing, and the like, either alone or in combination, in the drying furnace 8.

Phase inversion occurs between the solvent and other constituents (for example, acetone and water) in the drying process after the coating solution (5) is applied, and at the same time, the inorganic particles, the water-soluble polymer, and the particulate polymer are bonded to each other, It is possible to form aggregates.

At this time, the process from the immersion to the drying can be performed in an environment having an absolute humidity of 13 g / m ³ or less. When the immersion and the coating layer are formed under the above humidity conditions, the influence of moisture on the distribution of the binder in the separator is reduced and a separator having improved peeling force and air permeability can be obtained.

Hereinafter, a method of manufacturing a separation membrane according to another embodiment of the present invention will be described with reference to FIG. According to another embodiment of the present invention, the manufacturing process of the separator according to one embodiment of the present invention and the manufacturing process of the separator according to one embodiment of the present invention are substantially the same as those of the first embodiment, except that the base film 2 coated with the coating liquid is contacted with at least one pattern bar 6. [ The description will focus on the process of bringing the pattern bar into contact with the pattern bar.

The contact with the pattern bar 6 can be performed in the step of removing the excess coating liquid 7 before drying so that a part of the coating liquid 5 is removed to control the thickness of the coating layer or to flatten the surface of the coating layer .

When the separator is coated using the pattern bar 6, an amorphous pattern may be formed on the surface of the coating layer after drying the coating solution (FIG. 2).

Specifically, the surface of the coating layer may be divided into a first region 10 formed of a plurality of amorphous patterns adjacent to each other or spaced apart at a predetermined interval, and a second region 12 filling a space between the amorphous patterns, The first region 10 may contain more inorganic particles than the second region

More specifically, the first region 10 includes more inorganic particles than the second region and is relatively bright. The second region 12 includes more binders than the first region, And may be formed so that each region is distinguishable.

The form in which the first region 10 and the second region 12 are distinguished is not particularly limited and corresponds to a modification suitable for achieving the object of the present invention.

The first region 10 and the second region 12 formed on the coating layer of the separation membrane can be observed through a scanning electron microscope (SEM) photograph taken, for example, by enlarging the surface of the coating layer 400 times.

It can be formed so that the respective regions are divided in the drying process after coating using the pattern bar 6, so that the microvoids formed between the aggregates can be prevented. Since the solvent can be evaporated and dried through the micropores to form pores, excellent air permeability can be secured.

In addition, since pores are easily formed, the desired air permeability can be obtained even under low absolute humidity conditions. That is, the pattern bar 6 can be used to form an amorphous pattern divided into a first region and a second region on the surface of the coating layer, thereby increasing not only the peeling force but also the air permeability (FIG. 3).

The surface of the pattern bar 6 may be regularly arranged (for example, Fig. 5). A solid figure is a polyhedron in which the figures of the polygon are not on the same plane; And a rotating body formed when a planar shape is rotated by one axis about one straight line. Non-limiting examples of the polyhedron include a tetrahedron such as a triangular pyramid; Triangular prism, quadrangular pyramid; Square pillar, quadrangular pyramid, and the like. Non-limiting examples of the rotating body include a cone, a cylindrical truncated cone, and a sphere.

One side (e.g., bottom or side face) of the stereogram can be attached to the surface of the bar to form a pattern on the surface of the bar, and the bottom face of the stereogram can be polygonal or circular.

In the present invention, the term 'bottom surface' means two parallel surfaces in a three-dimensional shape, and 'side surface' means a surface perpendicular to the bottom surface.

In addition, the outer diameter of the pattern bar 6 may be 0.3 to 2 inches, for example, 0.5 to 1.5 inches, and the interval between the patterns formed on the surface of the pattern bar 6 may be 400 to 800 탆 , Specifically 500 to 700 mu m.

According to another aspect of the present invention, there is provided an electrochemical cell including a positive electrode, a negative electrode, and an electrolyte, and a separator interposed between the positive electrode and the negative electrode, wherein the separator is formed of any one of the embodiments of the present invention It is possible to provide an electrochemical cell, which is a separation membrane of one term. The type of the electrochemical cell is not particularly limited and may be a battery of a kind known in the technical field of the present invention.

The electrochemical cell of the present invention may be a secondary battery, specifically, a lithium secondary battery such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. The method for producing the electrochemical cell of the present invention is not particularly limited and a method commonly used in the technical field of the present invention can be used. A non-limiting example of the method for producing the electrochemical cell is as follows: After the polyolefin crab separator containing the organic and inorganic mixture coating layer of the present invention is placed between the anode and the cathode of the battery, The battery can be manufactured by filling.

The electrode constituting the electrochemical cell can be produced by binding an electrode active material to an electrode current collector by a method commonly used in the technical field of the present invention. The cathode active material is not particularly limited, and a cathode active material conventionally used in the technical field of the present invention may be used. Non-limiting examples of the positive electrode active material include lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, and lithium composite oxide in combination thereof. Of the electrode active materials used in the present invention, the negative active material is not particularly limited, and the negative active material conventionally used in the technical field of the present invention may be used. Non-limiting examples of the negative electrode active material include a lithium adsorbent material such as lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite or other carbon materials, and the like .

The electrode current collector used in the present invention is not particularly limited, and electrode current collectors commonly used in the technical field of the present invention can be used. Non-limiting examples of the positive electrode current collector material among the electrode current collectors include aluminum, nickel, or foil produced by a combination of these materials. As a non-limiting example of the cathode current collector material of the electrode current collector, copper, gold, nickel, a copper alloy, or a foil produced by a combination of these materials can be used.

The electrolytic solution used in the present invention is not particularly limited, and electrolytic solutions for electrochemical cells commonly used in the technical field of the present invention can be used. The electrolytic solution may be a salt having a structure such as A ⁺ B ^- dissolved or dissociated in an organic solvent. Non-limiting examples of the A ⁺ include alkali metal cations such as Li ⁺ , Na ^+, or K ⁺ , or cations made of combinations thereof. Non-limiting examples of B ^- include PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N ₃ SO ₂ ) ₂ ^- or C (CF ₂ SO ₂ ) ₃ ^- , or an anion composed of a combination of these.

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

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

Example  One

A coating liquid prepared by mixing the following first polymer solution, second polymer solution, inorganic dispersion, acetone and DMAc at a predetermined weight ratio on the surface of the polyethylene base film (SKI PE) having a thickness of 12 占 퐉 in contact with the anode of the battery was applied to both surfaces of the base film To prepare a porous separator having a coating layer formed thereon.

(1) Preparation of first polymer solution and second polymer solution

A polyvinylidene fluoride-hexafluoropropylene copolymer (9300, manufactured by Kuraray Co., Ltd.) having a weight average molecular weight of 700,000 (Mw) g / mol was added to acetone (purified gold) in an amount of 10% by weight, And the mixture was stirred at a temperature of 25 캜 to prepare a first polymer solution. Separately from the first polymer solution, polyvinylidene fluoride-hexafluoropropylene copolymer (21216, manufactured by Solvay Co., Ltd.) having a weight average molecular weight of 1 million (Mw) g / mol was dissolved in acetone (purified gold) and DMAc Purified gold powder) was added in an amount of 10 wt%, and the mixture was stirred in a stirrer for 4 hours at a temperature of 25 ° C to prepare a second polymer solution.

(2) Preparation of Inorganic Dispersion

Al ₂ O ₃ of 500 nm was added to 25 wt% of acetone (LS235, Japan) and milled at 25 캜 for 3 hours using a bead mill to prepare an inorganic dispersion.

(3) Preparation of coating liquid

The first polymer solution, the second polymer solution, the inorganic dispersion and acetone (purified gold) were mixed in a weight ratio of the first polymer solution: second polymer solution: inorganic dispersion: acetone: DMAc = 1.10: 1.10: 8.80: 85.42: 3.58 And the mixture was stirred with a power mixer at 25 DEG C for 2 hours to prepare a coating solution.

(4) Preparation of membrane

A polyethylene-based film having a thickness of 12 占 퐉 was immersed in a coating solution, and the immersed separating membrane was raised from the coating solution to apply the coating solution to both surfaces of the substrate film. Then, the excess coating solution was removed using a semi-cylindrical pattern bar And the coating solution was dried to prepare a separation membrane having a coating layer formed thereon.

Coating speed at the time of the coating is 20 mpm, the rotational speed of the pattern bar was 20rpm, within an absolute humidity of the coating chamber was an absolute humidity of ³ g / m 3, the temperature was 23 ℃, the drying step is 23 seconds drying time, drying temperature 120 Deg.] C, and an air velocity of 20 m / sec.

Example  2

A separation membrane was prepared in the same manner as in Example 1 except that the absolute humidity was 5 g / m ³ in (4) of Example 1 above.

Example  3

A separation membrane was prepared in the same manner as in Example 1 except that the absolute humidity was 7 g / m ³ in (4) of Example 1 above.

Example  4

A separation membrane was prepared in the same manner as in Example 1 except that the absolute humidity was 9 g / m ³ in (4) of Example 1 above.

Example  5

A separation membrane was prepared in the same manner as in Example 1 except that the absolute humidity was 11 g / m ³ in (4) of Example 1 above.

Example  6

A separation membrane was prepared in the same manner as in Example 1 except that the absolute humidity was 13 g / m ³ in (4) of Example 1 above.

Example  7

In (1) of Example 1, in order to prepare a polyamic acid solution instead of the first polymer solution and the second polymer solution, a three-necked flask was charged with 3,3'-diaminodiphenylsulfone (3,3'-diamino diphenyl sulfone) of 0.5 mol and N, N-dimethylacetamide (DMAc) were added and dissolved with stirring. Subsequently, 0.4 mol of pyromellitic dianhydride in solid state and 0.1 mol of 4,4'-hexafluoroisopropyldiphthalic acid dihydride (4,4 '- (hexafluoroisopropylidene) diphthalic anhydride) were added to the solution and stirred vigorously . The solid content at this time was 20% by weight, and the reaction was carried out for 24 hours while the temperature was kept below 25 ° C to prepare a solution containing polyamic acid having a weight average molecular weight of 60,000 to 80,000 g / mol.

The polyamic acid solution and the inorganic dispersion solution prepared in (3) of Example 1 were dispersed in a polyamic acid solution: N, N-dimethylacetamide (DMAc): inorganic dispersion: acetone = 0.9: 0.3: 4.7, and the mixture was stirred with a power mixer at 25 DEG C for 2 hours to prepare a coating solution.

A separation membrane was prepared in the same manner as in Example 1 except that the absolute humidity was 5 g / m ³ in (4) of Example 1 above.

Comparative Example  One

A separation membrane was prepared in the same manner as in Example 1 except that the absolute humidity was 15 g / m ³ in the coating layer forming conditions (4) of Example 1.

Comparative Example  2

(4) of Example 1 except that the pattern bar was coated with a wire bar and the absolute humidity was 5 g / m ³ under coating layer forming conditions. Respectively.

The composition and coating conditions of the coating liquids used in Examples 1 to 7, Comparative Examples 1 and 2 are shown in Table 1 below.

Examples /
Comparative Example Coating method Composition (weight ratio) dry
time
(sec) dry
Temperature
( ^O C) coating
Temperature
( ^O C) never
Humidity
(g / m ³ ) PVdF-HFP Polyamic acid 1 million 70 million 60,000-80,000 Al ₂ O ₃ Acetone DMAc Example 1 Pattern bar 1.10 1.10 - 8.80 85.42 3.58 23 120 23 3 Example 2 Pattern bar 1.10 1.10 - 8.80 85.42 3.58 23 120 23 5 Example 3 Pattern bar 1.10 1.10 - 8.80 85.42 3.58 23 120 23 7 Example 4 Pattern bar 1.10 1.10 - 8.80 85.42 3.58 23 120 23 9 Example 5 Pattern bar 1.10 1.10 - 8.80 85.42 3.58 23 120 23 11 Example 6 Pattern bar 1.10 1.10 - 8.80 85.42 3.58 23 120 23 13 Example 7 Pattern bar - - 9.00 41.00 47.00 3.00 23 120 23 5 Comparative Example 1 Pattern bar 1.10 1.10 - 8.80 85.42 3.58 23 120 23 15 Comparative Example 2 Wire bar 1.10 1.10 - 8.80 85.42 3.58 23 120 23 5

Experimental Example  One

The thickness of the coating layer and Porcelain  Measure

The following methods were performed to measure the thickness and the coating amount of the coating layer of the separation membrane prepared in the above Examples and Comparative Examples.

First, the thickness of each coating layer was measured using an SEM cross section image of each coating layer and a micro caliper. Then, each of the coating layers was cut into a size of 10 cm × 10 cm × TD, and the weight was measured with an electronic scale to calculate a coating amount. The results of the measurement of the thickness and the coating amount are shown in Table 2 below.

Experimental Example  2

Measurement of air permeability of membrane

The following methods were performed to measure the air permeability of the separator prepared in the Examples and Comparative Examples.

Ten pieces of specimens were cut from 10 different points and then a 100 cm diameter circular membrane of 100 cm in diameter was made from each of the above specimens using an air permeability measuring device EG01-55-1MR (manufactured by Asahi Seiko Co., Ltd.) The average time taken for permeation was measured five times each, and the average value was calculated to measure the air permeability.

Experimental Example  3

Separator Heat shrinkage  Measure

The following methods were performed to measure the heat shrinkage of the separator prepared in the Examples and Comparative Examples.

Each of the separation membranes prepared according to the above Examples and Comparative Examples was cut into 5 cm (MD) 5 cm (length) (TD) 5 cm to prepare seven samples. Each of the samples was stored in a chamber at 150 ° C for 1 hour, and the degree of shrinkage in the MD and TD directions of each sample was measured, and the average value of the shrinkage was measured.

Experimental Example  4

Between the coating layer and the substrate film Peel force  Measure

Each of the coating layers prepared in the above Examples and Comparative Examples was cut into 1.5 cm (width) × 7 cm (length) (TD) to prepare 10 samples. Each of the above samples was firmly attached to a glass plate using a transparent double-sided tape (3M), and then a force required to peel each coating layer using a universal test machine (UTM) was measured. And the peel force was measured.

Experimental Example  5

Observation of surface of coating layer

Each surface of the coating layer of the separator prepared in the above examples and comparative examples was observed at 400x magnification using SEM.

The first region appears to contain more inorganic particles than the second region, and each region is distinguished by a second region which is darker than the first region by including more binder (FIG. 2).

At this time, when the first regions were adjacent to each other or spaced apart from each other by a predetermined distance, it was judged that "amorphous pattern formation"

Among them, a photograph of the surface of the coating layer according to Example 2 is shown in Fig. 3 (x400 times), and a photograph of the surface of the coating layer according to Comparative Example 2 is shown in Fig.

The measurement results according to Experimental Examples 1 to 5 are summarized in Table 2 below.

Examples /
Comparative Example Thickness (㎛) Coverage
(g / m ² ) Ventilation
(sec / 100cc) Heat Shrinkage (%) Peel force
(gf / cm) Coating layer
surface Base film One side of the coating layer TD MD Example 1 12 2.65 7.16 250 2.4 3.2 651 Amorphous pattern formation Example 2 12 2.45 6.88 234 3.5 3.9 639 Amorphous pattern formation Example 3 12 2.55 7.09 221 4.6 4.8 463 Amorphous pattern formation Example 4 12 2.7 7.33 206 6.4 6.9 348 Amorphous pattern formation Example 5 12 2.6 6.98 189 7.3 7.5 221 Amorphous pattern formation Example 6 12 2.6 6.98 177 6.9 7.1 210 Amorphous pattern formation Example 7 12 2.6 6.98 245 0.9 1.0 620 Amorphous pattern formation Comparative Example 1 12 2.65 7.24 173 7.8 8.4 30 Amorphous pattern formation Comparative Example 2 12 2.6 7.08 1000 8.9 10.7 28 Pattern formation

As shown in Table 2, when the absolute humidity is 13 g / m ³ or less and the pattern bar is used (Examples 1 to 7), the first region in which the inorganic particles are dense and the second region in which the binder is dense are separated, Thereby forming amorphous patterns in which regions are adjacent to each other or spaced from each other (FIG. 3). In addition, in the case where the absolute humidity was 13 g / m ³ or less (Examples 1 to 7), the peeling force was improved by increasing the adhesive force as compared with the case where the absolute humidity was more than 13 g / m ³ (Comparative Example 1) It was confirmed that the shrinkage of the separator due to the low heat resistance was excellent.

Further, it was confirmed that the use of the pattern bar was superior to the case of using the wire bar (Comparative Example 2, Fig. 4), in terms of air permeability.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that such detail is solved by the person skilled in the art without departing from the scope of the invention. will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

1 Base Film Supply Unit
2 base film
3 rolls
4 baths
5 Coating solution
6 wire bar or pattern bar
7 extra coating solution
8 drying furnace
10 First area
12 second region

Claims (16)

The polyolefin-based porous substrate film and
And a coating layer containing a binder and inorganic particles formed on one or both sides of the substrate film,
The peel force of the coating layer on the polyolefin-based porous base film is 50 gf / cm or more,
The heat shrinkage measured after leaving the separator at 150 ° C for 1 hour is 10% or less in each of MD (Machine Direction) and TD (Transverse Direction)
The separation membrane has an air permeability of 150 to 300 sec / 100 cc,
Wherein the surface of the coating layer comprises a first region consisting of a plurality of amorphous patterns adjacent to each other or spaced apart at a predetermined interval; And
And a second region filling a space between the amorphous patterns,
Wherein the first region comprises more inorganic particles than the second region. The separator according to claim 1, wherein the peel force is 100 gf / cm or more. The separation membrane according to claim 1, wherein the peeling force is 400 gf / cm or more and the heat shrinkage rate is 5% or less in the machine direction and the perpendicular direction, respectively. The separator according to claim 1, wherein the binder is polyamic acid. 5. The membrane according to claim 4, wherein the polyamic acid has a weight average molecular weight of 20,000 to 100,000 g / mol. The separation membrane according to claim 1, wherein the binder comprises two or more kinds of binders having different weight average molecular weights. 7. The membrane of claim 6, wherein the binder comprises a binder having a weight average molecular weight of less than 900,000 g / mol and a binder having a weight average molecular weight of greater than 900,000 g / mol. 8. The membrane of claim 7, wherein the binder comprises a polyvinylidene fluoride-hexafluoropropylene copolymer. delete The polyolefin-based porous substrate film and
And a coating layer containing a binder and inorganic particles on one side or both sides of the substrate film,
The absolute humidity in the coating chamber during the production of the separator is 13 g / m ³ or less,
Wherein the surface of the coating layer comprises a first region consisting of a plurality of amorphous patterns adjacent to each other or spaced apart at a predetermined interval; And
And a second region filling a space between the amorphous patterns,
Wherein the first region includes more inorganic particles than the second region. The method for producing a separation membrane according to claim 10, wherein the absolute humidity is 11 g / m ³ or less. The method for producing a separation membrane according to claim 10, wherein the coating layer comprises: immersing the base film in a coating solution to apply the coating solution to the base film, removing the excess coating solution using a pattern bar, and then drying to form a coating layer . delete An anode, a cathode, and an electrolyte,
An electrochemical cell including a separator interposed between the positive electrode and the negative electrode,
Wherein the separation membrane is a separation membrane according to any one of claims 1 to 8 or a separation membrane produced by the method according to any one of claims 10 to 12. 15. The electrochemical cell of claim 14, wherein the electrochemical cell is a secondary cell. The electrochemical cell according to claim 15, wherein the secondary battery is a lithium secondary battery.

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